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Unit-1-Computer System

Unit-2- Number System and Conversion Boolean Logic

Unit-3-Computer Software and Operating System

Unit-4-Application Package

Unit-5-Programming Concepts and Logics

Unit-6-Web Technology

Unit-7-Multimedia

Unit-8-Information Security and Cyberlaw

IMP Questions

Final Exam-IMP Questioins For Computer-Grade-XI.docx

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Unit Wise Important Questions for Computer Science XI

Unit 1 Computer System

• Unit Wise Important Questions for Computer Science XI

  Unit 1 Computer System                                                                                          

  • What is Generation of computer? Explain briefly about different generation of computer.
  • What is computer? Explain characteristics of computer.
  • What are the application fields of computer? Explain in brief.
  • Why computer in known as versatile and accurate machine? Explain
  • Differentiate between 3G and 4G computer.
  • Explain the application areas of computers.
  • List out the merits and demerits of computer.
  • Differentiate between Analog and digital computer.
  • Differentiate between Micro and Super Computer.
  • Differentiate between IBM Compatible and IBM Computer.
  • What is super computer? Explain its application in real time situations.
  • Differentiate between RAM and ROM.
  • Differentiate between impact and Non-impact printer.
  • Differentiate between primary memory and Secondary memory.
  • Differentiate between CRT and LCD
  • Differentiate between CD and DVD.
  • Define software. Explain the different types of software in detail.
  • Explain the functions of CPU.
  • What is bus? Explain its types with clear diagram.
  • What is virus? What are the symptoms of virus? Write its examples.
  • Write Short notes on:
    1. Cache Memory b) Virtual Memory     C) Buffer        d) Microprocessor
    2. e) Hard disk f) Input device g) Dot-Matrix printer   h) interface or Port
    3. i) Charles Babbage j) Lady Augusta Ada k) V. Neumann
    4. l) Mark I m) Napier’s bone n) ABC    o) UNIVAC     p) EDVAC    q) Howard Aiken
    5. r) Hybrid computer s) Personal computer             t) Mainframe computer

   

  Concept of computer

  The word computer is derived from the Latin word ‘computare’ which means to calculate or the word computer is comes from the English word ‘compute’ which means to calculate. So that computer is a calculating device.

   

  Introduction of Computer

  The word “Computer” is derived from the Latin word “Computare” which means ‘to calculate’. Nowadays, computer has become an indispensable part of our life. Computer is used in various places like: home, school, college, offices etc. Computer can perform complex mathematical calculations accurately in a short period of time. The modern computer has lots of capabilities like creating documents, videos, games, music presentation, etc. It can use AI (Artificial Intelligence) for understanding natural language, taking self-decision capabilities, analyzing graphs and patterns, etc.

  • A computer is an electronic device that accepts raw data and instructions from users; processes it according to the given set of instructions, stores and gives meaningful information.
  • Computer is an electronic device that accepts raw data and instruction, store it, process it and produce meaningful information.
  • Computer is an electronic device that receives raw data and instruction, store it, process it according to the given set of predefined instructions and them gives the meaningful information as a result.
  • A computer can be defined as a multipurpose, programmable, electronic data processing device that is capable of accepting input (data), processing it and producing a refined data (information) output at high speed.
  • Computer is an electronic device which can perform computation as well as logical action at high speed.
  • Computer is a high speed electronic digital data processing device.
  • Computer is a multi-tasking programmable electronic machine which performs the calculations and processes information with very high speed.

  Computer Means

  • C= Commonly
  • O= Operating
  • M= Machine
  • P= Purposed by
  • U= Unlimited
  • T= Technology for
  • E= Education and
  • R= Research

   

  Working of a computer/General function or Basic Operation of Computer

  1. Inputting: It is the process of entering data and instruction into computer system.
  2. Processing: It is the process of performing arithmetic and logical operation.
  3. Storing: It is the process of saving or holding data, information and programs for future use.
  4. Outputting: It is the process of producing useful information as a result.

   

  Some basic terms

  1. Data: It is the collection of raw facts and figures about a person, place, and things etc. which can be recorded in the form of text, number, sound or image. Example, ram, 102, male etc.
  2. Instruction: It is a command given to the computer to do s specific task.
  3. Information: It is the processed form of data which we get in the required form. So it is very meaningful and useful to us.
  4. Process: Processing is the conversion of inputted data into output (information) which is done by the processing unit of the computer.
  5. Program: Program is set of instructions to perform specific task in a computer, a component of software.
  6. Software: Software is the collection of computer programs to perform special work in a computer. Software tells the computer how to do and what to do.
  7. Hardware: It is the physical parts of computer system which can be touch, felt and seen.
  8. Input: It is data and instruction entered into computer for processing.
  9. Output: It is called result or information.
  10. Memory device: The device which is used to store data, instruction and information (temporarily or permanently) is called memory device. Examples are RAM, ROM, Hard Disk, Pen drive etc.

   

  Characteristics of a Computer / Features of Computer

   A computer is powerful and useful in all areas. The use of computer is increasing with time. The main features or characteristics of computer are described below:

   

  1. Automatic

  A computer is an automatic device. It can do tasks automatically as instructed by software. It can automatically control various devices attached with computer system.

  2. Speed

  The calculation in the computer is at very high speeds. For example, a micro-computer can perform millions of instructions per second as many times without any mistake. The speed increases, as the power of computer increase. For example, a super computer can operate at speed measures on nanoseconds and even picosecond.

  A computer performs tasks accurately. The operations on data in computer are performed through electronic circuit according to given instructions. Computer can perform millions and billions of operations on data within a second. The speed of computer is measured in MegaHertz (MHz) or GigaHertz (GHz). The time taken to perform a task is measured in fraction of second.

  3. Accuracy

  A computer performs tasks accurately. If data and instructions given to the computer are correct then it gives an accurate output. It means output totally depends on the given instructions and input data. If input data is incorrect then the output will be incorrect which is called GIGO (Garbage in Garbage out).

  4. Storage:

  Computer system consists of data storage unit. A computer has main storage and secondary storage. A large amount of data can be stored in secondary storage like hard disk, pen drive, CD/DVD, etc. for future use. The main memory (RAM) stores currently used data. Computer stores data in term of 0 and 1.

  0 or 1	1 Bit
  4 bits	1 Nibble
  8 bits	1 Byte
  1024 bytes	1 Kilobytes (KB)
  1024 Kilobytes	1 Megabyte (MB)
  1024 Megabytes	1 Gigabytes (GB)
  1024 Gigabytes	1 Terabytes (TB)
  1024 Terabytes	1 Petabyte (PB)
  1024 Petabytes	1 Exabyte (EB)
  1024 Exabyte	1 Zetta byte (ZB)
  1024 Zetta byte	1 Yotta byte (YB)
  1024 Yotta byte	1 bronto byte (BB)

  5. Diligence

  A computer can continuously work for a long time without losing its speed and accuracy. So it is called diligent device. It doesn’t get tired or bored or lazy while working.

  6. Versatile

   A computer is a versatile device which means it is flexible. It has capability of performing different types of tasks like drawing paints, playing games, music, calculations, sending an e-mail, desktop publishing work, etc. in different field efficiently. So it is used in different fields to perform varieties of tasks.

  7. Reliability

  Computers are used widely as they are reliable. The computer never gives the wrong result as long as the input is given correctly. The probability of error in the computer is negligible. A Huge amount of verities of data like monetary transaction, banking account, personal information is stored in a computer with the strong reliability to the computer.

  Advantages and disadvantages of computer

  Advantages

  1. The computer can perform a complex operation in a short time.
  2. The computer can process a large volume of data.
  3. Computer can work continuously for a long time
  4. A single computer can perform multiple tasks such as watching a movie, playing games, listening song and others.
  5. The computer does not make a mistake.
  6. Computer increases the curricular performance of the student.

  Disadvantages

  1. The computer does not have a brain and cannot decide itself.
  2. It does not have its own intelligence.
  3. The computer does not have emotion and feelings.
  4. It needs electricity to operate.
  5. It cannot operate itself, unless, a human command is given.

  Application of computer

  A computer is given great importance in every field of work. Nowadays, it is impossible to find where computer are not used. Computer and its technology are used in education, agriculture, industries, banking, engineering, scientific research and many more. The main applications of computer are described below.

  1. Home
  2. Education
  3. Industry
  4. Business
  5. Bank
  6. Communication
  7. Health and Medical Field
  8. Computer In Graphics
  9. Desktop publishing
  10. Scientific Research
  11. Defense
  12. Entertainment

  Application of computer

  Computers at Home

  Computers have already changed our lives at home. New gadgets such as automatic washing machines, dishwashers and microwaves have made our lives easier. Many of the educational software programs are used by children at homes. These programs enrich students’ knowledge and skills. Encyclopedia, dictionaries, telephone directories and medical references are now available in optical disk which contains multimedia capabilities. Internet connections also provide electronic mail, discussion groups, and other communication options for home users. Apart from learning, computers also offer a new form of entertainment. They are used for playing computer games.

   

  Computers in Education

  Computers are used as teaching aids, research tools and analyzing systems in educational institutions. Teachers use computers to organize and prepare course materials. Teachers may use pictures, graphs and graphical presentations to easily illustrate a difficult concepts. Nowadays more and more educational institutions are using computer-assisted instruction systems. It offers interactive instruction on a one-to-one basis and can be automatically modified to suit the user’s level of ability. Educational software has become a major influence at all levels from elementary schools to universities. Elementary and secondary schools are using computers to play multimedia educational programs and to teach kids to explore the Web for information. A computer’s voice recognition capabilities and its connection to the Internet makes it possible for distance learning.

   

  Computers in Medicine

  Computers have played very important roles in the growth and improvement of health care. They are used in medicine to keep the records of patients’ case-histories, diagnosis and treatment of diseases. They are also used to monitor vital data during surgery in the operating theatre. They provide a complete, accurate, up-to-date and readily available source of information about patients’ health. Many medical scanners for exploring inside the body only work because of computer power. They are also used to monitor the availability of bed, staff payroll, hospital accounting, patient billing, drug inventory and location of doctors and patients in large hospitals. They have reduced the barriers of distance and time via telemedicine and

  on-line access to laboratory test results and medical researches.

   

  Computers in Government

  Computer is also used by the government to collect, process and store vast amounts of information. The web sites of the different government departments provide information to the users. It is used for the filing of income tax return, paying taxes, online submission of water and electricity bills, for the access of land record details, etc.

   

   

  Computers in Industry

  Modern factories and industries cannot work without computers. They control huge numbers of machines, especially robot-type devices for creating, assembling and testing products and their components. Computers also help humans to control complex machines, such as power stations, ships and space crafts. Rows of levers and switches can be replaced with computers that take care of routine tasks automatically. This leaves the human operator free for more important decisions. Many industries now use Computer Aided Design (CAD) to develop products and Computer Aided Manufacturing (CAM) to produce them. Computers are used for inventory control, planning and process control.

   

  Computers in Law and Order

  Computers are used by lawyers to research and store volumes of cases and judicial proceedings in the computer. Law enforcement agencies from local police to international organizations use computers to store information about criminals and suspected criminals. Minute details of speech intonation, physical characteristics, criminal habits and finger prints can be matched for accurate detection through computers.

  Computer systems are used in conjunction with video cameras to provide internal surveillance and to ensure the safety of prisoners and officers.

   

  Computers in Entertainment

  Computers have now become an important part of the entertainment industry. They are widely used to create special effects in movies. They are used in editing movies and multimedia presentations. They help in composing, editing, recording and reproducing music and sound effects. They are used in sports to analyze the movements of sports persons and to find faults in the movements and optimize the movements so that maximum efficiency is achieved. They are used by sports professionals to analyze their techniques to find their strengths and weaknesses. They are used to simulate games and to try out different game strategies.

   

  Computers in Banks

  The banking business has been revolutionized by computer technology. They are used for various tasks such as online enquiry of customer’s balance, cheque verification, updating the balance, calculating interests and printing customer statements. Many leading banks have installed Automated Teller Machines (ATMs). These enable the customers to draw money from accounts, transfer money, obtain bank statements, etc. All these can be done using a special plastic card which is inserted into the input device of a computer. This also eliminates the need for a clerk. The list of applications of computers is so long that it is not possible to discuss all of them here. In addition to the applications of the computers discussed above, computers have also proliferated into areas like investments, stock trading, accounting, ticket reservation, military operations, meteorological predictions, social networking, business organization, police department, video conferencing and book publishing.

   

  Evolution of computer

  Evolution of computer is a study of past development of computer i.e. it is meant by the gradual improvements of accuracy, speed and efficiency of computers through generations, whereas generations of computers may be defined as the development of computer in an average period of time in which old computer technology may be replaced by newer technology.

  Ancient people lived on the earth for centuries without counting. Then, they started to count their ten figures. It became so difficult to live and to remember anything. These phenomena were gradually replaced by the use of stones, counting notches on sticks or marks on walls. The different generations are described below which has helped the humans for keeping records with the passing of time.

  1.) The Mechanical Era (Zeroth generation)

  The calculator of this age was developed by using mechanical components like wood, metal, stone, bone, etc. It was used for simple mathematical calculations. Some of the popular calculations used in this ages are:

  • Abacus

  In ancient period, it was used to calculate mathematical calculation. It was used for performing simple calculation like counting, addition, subtraction and multiplication of number. An abacus consists of a rectangular frame carrying a number of wooden rods. Mid-bar divides each of these rods in top unequal -upper and lower parts.

  Fig: Abacus

  The upper part is called heaven, whereas lower part is called earth. The heaven consists of two beads, whereas the earth part consists of five beads to each rod. The value of bead on heaven part is five and earth is one. Each abacus consists of nine or eleven or thirteen rods.

  • John Napier (1550-1617 AD)

  THE SCOTTISH mathematician John Napier first published the table of logarithms in 1614 AD. It was very used and consists of a large number of calculations.

  He invented bone rods and used bones to demonstrate by subtracting and multiplication by addition according to his principle. These are made of strips of bones on which numbers were carved and painted that`s why it is also called Napier’s bone.

  Fig: Napier bone

  • William Oughtred (1575-1660AD)

  It is a rectangular device-slide-rule. It was a calculating device based on the principle of a log. A rule consists of two graduated scales, one of which slips upon other. It is devised in such a way that suitable alignment of one scale against the other makes it possible to find products and quotient of any numbers.

  Fig: Oughtred ruler

  • Blaise Pascal (1623-1662AD)

  The man name Blaise Pascal, was a brilliant mathematician and religious thinker. Pascal made a mercury barometer and measured atmospheric pressure to assist his father in his work accounting. Pascal invented the first mechanical calculation machine in Paris.

  Fig: Pascal Calculator

  • Baron Gottfried Wilhelm Von Leibniz (1646-1716AD)

  He develops a new method of calculation called ‘Calculus’. He modified the masculine machine and invented a first calculator, Stepped Reckoner, which was able to perform automatic addition, subtraction, multiplication, division, but could find out square root. Each with nine teeth of varying lengths instead of wheels it was called ‘Leibniz Calculator’ or ‘Stepped Reckoner’.

   Fig : Leibniz Calculator

  • Joseph Marie Jacquard (1752-1834 AD)

  The french man, Joseph Marie Jacquard, was a textile manufacturer who invented a mechanism for automated weaving clothes for the textile industry at Lyon, in 1802 AD. This machine was used to automatically control weaving looms to facilitate the production of weaving cloth with complex patterns.

  Fig: Jacquard loom

  • Charles Babbage (1791-1871 AD)

  The English Professor and Mathematician, Charles Babbage, invented the Different Engine at Cambridge University, in 1822 AD. This machine can solve differential equations and calculate various mathematical functions. It is also called “Analytical Engine “.

  Fig: Analytical engine

  • Lady Augusta Ada Byron Lovelace (1515-1852 AD)

  The English intelligent and independent-minded woman, Lady Augusta, was a daughter of English poet Lord Byron and a very Great follower, assistant of Charles Babbage. Lady documents Babbage`s work and writes programs for Babbage.

  This plan is now regarded as the first computer program. That`s why, she was considered the first computer programmer and a software language developed by the US Defense Department, was named Ada in her honor.

  • Herman Hollerith (1860-1929 AD)

  An American Inventor, Herman Hollerith, also applied the Jacquard loom concept in computing and applies for patents for an automatic punch-card tabulating machine. He invented a machine knows as ” Tabulating Machine “. This device could process on the punch cards and perform census calculating faster than ever before.

  • John Von Neumann (1903-1975 AD)

  The Hungarian Mathematician, John gave an idea of stored program computer in the sense that program is stored internally in the main memory of the computer along with its associated data, in 1945. So, he is called the “Father of Stored Program”. Before that, program required for the computer were integrated and written permanently in chips. So, modification of program was not possible. But, after Neumann, such programs were stored on a computer in some storage media, so modification was easy and flexible.

  2.) The Electro-Mechanical Era

  The calculator of this age was developed by using mechanical and electronic component vacuum tube.
  Successful general purpose mechanical computers were built, in the 1930s. Konrad Zuse developed mechanical computer, the Z1, in 1983 in Germany.

   

  • The Mark I Computer (1937 – 1944)

  A Professor of Physics, Howard H. Aiken designed a general purpose mechanical computer at Harvard University and IBM Automatic Sequence Controlled Calculator (IBM ASCC). It was the first fully automatic calculating machine and later as Harvard Mark I.

  It used binary numbers for its operation. Later, Mark II was invented by Aiken and his colleagues that were working electromechanical relays for its operation. Mark II used 19000 valves.

  • The Mark II Computer

  It used about 18 thousand vacuum tubes as the main memory device with 7 lakes 50 thousand parts. It is 51 feet long, 8 feet height and 3 feet wide as bulky in size. It was capable of performing five basic arithmetic operations; additions, subtraction, multiplication, division and table reference. The result was printed at the rate of one result per five seconds.

  • The Atanasoff-Berry Computer (1939 – 1942)

  In 1939, John Vincent Atanasoff and Clifford Berry designed Atanasoff-Berry computer or ABC solving systems of mathematical simultaneous equation. It used 18000 valves and other 45 valves for internal logic and capacitors for storage.

  It used punch cards as input and output operation i.e secondary. It is considered as the first computing machine which introduced the idea of binary arithmetic, regenerative memory and logic circuits.

   

  • The Colossus (1941 – 1944)

  In 1944, Colossus computer is designed by Alan M. Turing and build by British mathematician Alan Mathison Neuman, Alan with some colleagues, creates a computer named colossus at the University of Manchester, England, which comprised 1800 vacuum tubes.

  It was one of the world’s earliest working programmable electronic digital computers. Colossus was a special purpose machine that suited a narrow range of tax (for example, it was capable of performing decimal multiplication).

  • The Electronic Computer Era

  The computers of this age are developed by using electronic components like a vacuum tube, transistors IC, VLSI, etc. These computers are smaller, faster and more reliable.

  • The ENIAC (1943-1946)

  In 1946, John W. Mauchly and J.presper Eckert constructed ENIAC (Electronic Numerical Integrated and Calculator), at the Moore School of Engineering of the University of Pennsylvania. USA ENIAC was the first popular general purpose all electronic digital computers. John Von Neumann was the consultant of the ENIAC project.

  It was a very large machine weighing about 30 tons and containing about 17,468 vacuum tubes, 70,000 resistors, 5 million soldered joints and it consumed 160 kilowatts.

   

  • The EDVAC (1946-1952)

  EDVAC (Electronic Discrete Variable Automatic Computer) was developed by Dr.John Von Neumann,and a member of the Moore School of Engineering of the Unversity of Pennslyvania,J.P Eckert, and J.W Mauchly. The EDVAC is used for more school personnel and the Ballistics Research Laboratory of the US Army,which was based on John Von Neumann`s ideas of Stored Program”.

  • The UNIVAC (1951)

  UNIVAC (Universal Automatic Computer) was developed by J.P.Eckert and J. Mauchly in 1951. It was the first computer manufactured for commercial use and general purpose digital computer. It was designed to handle both numeric and textual information. Before this, all the computers were either used for defense or census was by General Electrical Corporation in 1954.

  Generation of Computers

  Computer generation is the classification of computers into different groups according to their manufacturing date, memory device, and other hardware and software technology used inside those computers. Generation of computer is a step in developing (advancing) technology.

   

  The classification, time periods and main device are given below:

  Generation	Time Duration	Memory device used
  First	1945-1955	Vacuum tubes and valves
  Second	1957-1963	Transistor
  Third	1964-1971	ICs
  Fourth	1972 onward	VLSI or Microprocessor
  Fifth	Present and future	Bio- chips

   

  Summary table of computer generation:

  Features	First	Second	Third	Fourth	Fifth
  Electronic Device	Valve/ Vacuum tube	Transistor	IC	Microprocessor	Bio-Chips
  Speed	Milli Second	Micro Second	Nano Second	Pico Second	More than femto second
  Internal Memory	Valve	Magnetic core	Semi Conductor	Semi Conductor	Super conductor
  Permanent Storage	Punched Cards	Magnetic Tapes	Magnetic Disk( FDD)	Magnetic and Optical Disks (HD,CD,DVD, Pen Drive)	New Technology for storage
  Computer Language	Fully Machine	Assembly and little bit of High	Fully High Level	High Level and 4GL	Natural Language
  Cost, Size, Electrical consume, Heat generate	Very High	High	Low	Very Low	Not Known
  Speed, Capability	Very less	Less	Moderate	High	Much higher

  1.) First Generation Computer (1945-1955)

  Fig: First Generation Computer

  Features of first generation computers:

  • Technology used: vacuum tube
  • Machines languages were used to instruct the computer.
  • Magnetic core memory was used as primary memory.
  • Electrostatic tubes, Paper tape, punch card, magnetic tape
  • Punched card, printing devices were used for input/output operations and store the result.
  • It occupies very large space, slow processing, inefficient and unreliable due to low accuracy.
  • Power consumption was very high and it generated much heat.
  • It could only perform straight forward simple numerical calculation.
  • Computer used to be much expensive.

  The example of first generation computers is ENIAC, UNIVAC, EDVAC, and EDSAC.

  2.) Second Generation Computer (1957-1963)

  Fig: Second Generation Computer

  Some of its features are:

  • Technology used: Transistor
  • Operating speed was in terms of a microsecond.
  • Assembly language and machines independent language such as COBOL (Common Business Oriented Language) and FORTRAN (Formula Translation) were introduced the size of the computer.
  • Magnetic core memory was used as primary memory.
  • Magnetic drum and magnetic tape were used as secondary memory.
  • Power required to operate them was low.
  • It could perform scientific calculation such as solving differential equations.
  • Storage capacity and use of computers are increased.

  3.) Third Generation Computer (1964-1971)

  Fig: Third Generation Computer

  Features of the third generation computers are:

  • The technology used: IC (Integrated Circuit).
  • Transistors were replaced by IC in their electronic circuitry.
  • High-level languages like FORTAN, BASIC and other are used to develop programs.
  • Semiconductor memory like RAM and ROM were used as primary memory.
  • Monitor and keyboard were introduced for data input and output respectively.
  • Multiprogramming facility was developed.
  • The computer was used in census calculation, military, banks and industries.
  • Size, cost, power requirement and heat generation decreased.
  • Processing speed and storage capacity used of computer increased.

  4.) Fourth Generation Computer (1972 onward)

  Fig: Fourth Generation Computer

  The invention of microprocessor chip marked the beginning of the fourth generation computers. Semiconductor memories replaced magnetic core memories. The invention of microprocessors led to the development of microcomputer or the personal computer.

  The first microprocessor called Intel 4004 was developed by American Intel Corporation 1971.

  Features of the fourth generation computer are:

  • Technology in use: VLSI is introduced and used Microprocessor-based technology.
  • Problem-oriented fourth generation language (4GL) is used to develop the program.
  • Semiconductor like RAM, ROM and cache memory is used as a primary memory.
  • Magnetic disks like hard disk, optical disk (CD, DVD), Blue-ray disk, flashes memory (memory chip, pen drive) are used as secondary memory.
  • E-mail, Internet and mobile communication are developed.
  • Advanced, user-friendly, web page software are developed.
  • Size, cost, power requirement, heat generation decreased compared to the previous generation.
  • Operating speed, storage capacity ,use of computer increased compared to the previous generation

  The example of the fourth generation computer is IBM-PC, HP laptops, Mac notebook etc.

  5.) Fifth Generation Computer (Present and future)

  Fig: Fifth generation Computer

  The aim is to bring machines with genuine IQ, the ability to reason logically and with real knowledge of the word. Thus, this computer will be totally different, totally novel and totally new than last four generations of computer.

  Fifth generation computer was based on Artificial Intelligence (AI) and that is still developing process, but not yet a reality i.e this computer is incomplete. The scientists are working on it still.

  These computers will be able to converse with people and will be able to mimic human sense, manual skills, and intelligence.

  Features of the fifth generation computers are:

  • Technology to be used: These machines will incorporate Bio-chip and VVLSI (Very Very Large Scale Integration) or Ultra-Large Scale Integration (ULSI)
  • The computer will have Artificial Intelligence (AI).
  • Natural language will be used to develop programs.
  • The computer will have parallel processing in full fledge.
  • The operating speed will be in terms of LIPS(Logical Inference per Second)
  • This aim is to solve highly complex problems, which require great intelligence and expertise when solved by people.
  • Quantum computation, molecular and nanotechnology will be used completely.

  AI (Artificial Intelligence):

  • It is a branch of computer science which concerned with programs that solves and analyze problems intelligently.
  • Artificial intelligence is the science of making machines imitates human thinking and behavior.

   

   

   

   

   

   

   

   

  1.4 Classification of Computer

   

  Classification of Computer
  On the basis of Purpose	On the basis of Size
  Ø  General Purpose Computer	Ø  Super Computer
  Ø  Special Purpose Computer	Ø  Mainframe Computer
  On the basis of Working principles	Ø  Mini Computer
  Ø  Analog Computer	Ø  Micro Computer
  Ø  Digital Computer	ü Desktop
  Ø  Hybrid Computer	ü Laptop
  On the basis of Brand	ü Handheld
  Ø  IBM PC	On the basis of Model
  Ø  IBM Compatible PC	Ø  XT Computer
  Ø  Apple/Macintosh Computer	Ø  AT Computer
  	Ø  PS/2 Computer

   

  Classification of Computer

  On the basis of

  Purpose

  Special purpose

  Micro computer

  Mini computer

  Mainframe

  Computer

  Super computer

  General purpose

  On the basis of size

  Hybrid Computer

  Digital Computer

  Analog Computer

  On the basis of

  Working principle

   

  On the basis of purpose

  1. General Purpose computer

  A general-purpose computer is a description of a computer capable of performing many different tasks rather than a specific one like a special-purpose computer. For example, the computer you’re using now to read this web page is a general-purpose computer. In addition to browsing the Internet, you can play a game, write a letter in a word processor, and other tasks.

  2. Special Purpose computer

  A special-purpose computer is embedded in almost all electronic devices and is the most widely-used computer. This computer is designed for a specific task and is found in ATMs, cars, microwaves, TVs, the VCR, and other home electronics. See our special-purpose computer page for further information and examples.

   

  S.N.	Special Purpose Computer	S.N.	General Purpose computer
  1	They are called single task.	1	They are also called multi task computer
  2	The program is installed at the time of manufacturing in it.	2	Programs are installed later on as per the requirement of user.
  3	A user cannot install program in it.	3	A user can install different programs according to their needs.
  4	Programs are permanently stored.	4	Programs are temporary in the memory.
  5	It is comparatively faster than general purpose computer.	5	It is comparatively slower than special purpose computer.
  6	Example: Washing machine	6	Example: Microcomputer.

   

  On the basis of Work:

  1) Analog Computer:- Analog computer is one which operates on continuous data, usually of a physical nature such as length, voltage or current, etc. An analog machine is usually a special purpose device dedicated to a single task. Analog computers are based on analog signals that are continuous signals.

  These types of computers were widely used in scientific and industrial applications. These are used in a hospital to measure the size of the stone in kidney and mental diseases diagnostics.

  Analog computer works by measuring rather than counting. It is usually used for scientific work rather than personal purpose and commercial use so it is special purpose computer. It is powerful in solving differential equations.

   

  Characteristics of analog computer

  • Based on continuous varying data.
  • Measure only natural or physical values.
  • Used for special purpose.
  •  
  • Generally, no storage facility is available because they work on real time basis. If provided, then only a little amount of storage is available in it.
  • Accuracy of these types of computer is very less because of noise and filtering facility.

  Examples: – ohmmeter, speed meter, tetrameter, seismograph etc.

   

  2) Digital Computer:-                                                                        

  The computer which works on discrete data or discontinuous data is known as a digital computer. It works on a binary system where 0 represent off and 1 represents on. It is based on digital signals i.e discrete signals.

  So, the basic principle of these computers is either present or absence of an electric pulse in the signals. It is a multipurpose and programmable computer. It is fast processing, more accurate and has large memory capacity. It is usually general purpose computer. Some examples of a digital computer are IBM PC, Apple/Macintosh computer, etc.

  
  

  Characteristics of digital computer

  • Based on discrete data which are not continuous with time.
  • Based on principle of logic 1 and 0 or high and low voltage.
  • Used for general purpose.
  • They are more reliable because of less noise and filtering facility.
  • It has large memory capacity because the calculations are to be stored internally for future use and re-programming.
  • It is multipurpose and programmable so, it is of high cost and faster processing.
  • Signal representation of digital pulse is as follows.

  Example: – IBM PC, Apple/Macintosh etc.

   

  3) Hybrid Computer:-

  A computer, which has a combination best feature of both analog and digital computers, is called a hybrid computer. It helps the user to process discrete and continuous data. The hybrid computer can convert the analog signal into digital signals and digital signal into analog signal. Hybrid computers are used mainly in specialized applications where both kinds of data need to be processed. Therefore, they help the user to process both continuous and discrete data.

  Characteristics of Hybrid computer are as follows.

  • It is the combination of qualities of analog as well as a digital computer.
  • It can process both continuous and discrete data.
  • It is special purpose computer.
  • It can convert one type of data into another.
  • It is mostly used in radar communication, rocket launching, weather forecasting and in other fields.
  • It usually high cost compared to analog and digital computer.
  • Hybrid Machines are generally used in scientific applications or in controlling industrial processes.

   

  S.N.	Digital Computer	S.N.	Analog Computer
  1	These computers work with digits.	1	These computers work with natural or physical value.
  2	It works upon discrete data.	2	It works upon continuous data.
  3	It operates by counting and adding, i.e. it calculates.	3	It operates by measuring and comparing.
  4	Its accuracy is high.	4	Its accuracy is low.
  5	Results are obtained after complete computation.	5	Output is continuous.
  6	It is general purpose in nature.	6	It is special purpose computer.
  7	Larger storage capacity (memory).	7	No any or smaller storage capacity.
  8	Higher cost then analog computer.	8	Lower cost than Digital computer.
  9	It can be reprogrammed.	9	Normally, it cannot be reprogrammed.
  10	Example: IBM PC, Apple etc.	10	Example: Presley, Speedometer etc.

   

  2.) On the basis of Size:

  1) Micro Computer:-

  These are the smallest computer systems on the basis of size. These computers are based on micro chips because microprocessor is used as memory device and they are very small. These computers are also called PC (personal computer) or home computers. The smallest of this category are laptop, notebook and palmtop computers. This size is reducing day- by-day.

  Characteristics of micro computer

  • Smallest in terms of size can be kept on top of a desk (desktop), on top of laptop and like a notebook.
  • Speed and cost is also smaller.
  • Since a single user system is used, storage devices and memory are smaller sized.

  Example: IBM Pentium Pc, Apple/ Macintosh etc.

  Types of Micro Computer

  1. Desktop Computer:  A Desktop computer is a personal computer that is designed to fit on top of a typical office desk.
  2. Laptop Computer:  A Laptop computer is a portable personal computer light and small enough to sit on a person’s lap.
  3. Handheld computer: It can fit one hand and we can operate it with the other hand. Because of its reduced size, the screen of handheld computer is quite small. Similarly, it also has small keyboard.

  – Notebook: Notebook is also designed for the people in move. But it is smaller in size compared to laptop. It is device with a reduced keyboard, screen, functionality, and software support than laptop.

              – Palm top:  A small computer that literally fits in your palm. Compared to full size computers, palmtops are severely limited, but they are practical for certain function such as phone books and calendars.

              – Tablet Pc:  A tablet PC is a wireless, portable personal computer with a touch screen interface. The tablet is typically smaller than a notebook computer but larger than a smart phone

              – Smart phone/ PDA:  A smart phone is a mobile phone that includes advanced functionality beyond making phone calls and sending text messages.

             

  2) Mini Computer:-

  Minicomputer is medium in size it is bigger than micro and smaller than mainframe computer. A centrally located server or CPU is connected with more than 50 terminals. At a time 50 people can work with single minicomputer for data processing, Desktop publishing etc. It is linked with network and used for Bank, Business field.

  Characteristics of mini computer

  • Medium sized computer occupying approximately 10 sq. feet of area.
  • More than 50 terminals and large capacity storage devices than micro computer.
  • But minicomputer is smaller than mainframe computer.
  • Used for general purpose.
  • Used in medium sized organizations and corporations for their database administration.

  Examples: – Prime 9755, vax 36 etc.

   

  3) Mainframe Computer:-

  These are the largest computer on the basis of the size. It has more storage capacity and fast processing speed. It takes about 100 sq. feet. At least 100 people can work at a time. A centrally located server or CPU is connected with more than 100 terminals.

   

  
  

   

  Fig. Mainframe computer

   

   

  Characteristics of mainframe computer

  • Largest in size with approximately 10000 sq. feet area.
  • Central processor, central administration
  • More than 100 terminals, large capacity storage devices used.
  • Fastest and very expensive system.
  • General purpose computer.
  • Used by large agencies and government for large scale data processing.

  Examples: – IBM 1401, ICL 2950/10 etc.

   

   

  
  

   

  4) Supper Computer:-

  Super computer is very large machine which works in MIPS. They are most powerful and expensive computers. They have extremely large storage capacities and processing speed is at least 10 times faster than other computer.

  Characteristics of super computer

  • It is very large and powerful computer.
  • It is large storage capacities and work is done by very fast.
  • It can calculate about 400 million numbers every second.
  • It can result is always exactly correct.
  • Super computers are used in weather forecasting

         petroleum engineering and medicine and for creating

         computer graphics.

  • It is used in weather research and scientific research.

  Some examples of the super computers are CRAY, NEC Super SX11, and CYBER 205 etc.

  
  

   

  Micro Computer	Super Computer
  1. It is less powerful.	3.      It is more powerful.
  2. It is the smallest computer on the basis of size.	2. It is larger in size.
  3. It is cheaper.	3. It is the most expensive computer.
  4. It can be handled by only one person.	4. It required numbers of experts to operate.
  5. It is used in office, house.	5. It is used in weather forecasting, Scientific research.
  6. Example are IBM PC, Apple/ Macintosh etc.	6. Example are CRAY I, CYBER 205 etc.

   

  1) IBM Computer (IBM PC):-

  IBM, which established by Dr. Herman Hollerith in 1923 AD, is the largest computer manufacturing company in the world till today. It is leading the market of mainframe and PCs. It uses the processors multimedia devices and some other hardware parts developed by some other Companies like Intel but use the principle of its own. So, all the computers developed by IBM Company are called IBM computers. Example: – IBM PC and IBM Compatible.

   

  2) Apple / Macintosh Computer:-

  Apple Corporation was established in 1970 AD is USA. Within these 3 decades. It has gone much forward and produced PCs with good qualities and user friendly. So, the entire computers that are developed by Apple Corporation are called Apple/Macintosh (Mac) computers. These computers are architecturally totally different than that of IBM’s. Not only hardware part, but their software architecture is also totally different. Software made for IBM PC can’t be run in Macintosh or vice versa. Floppy disks or hard disks formatted in one can’t be recognized by on other.

  3) On the basis of Brand:

   

  1) IBM Compatible:-

  The computers developed by IBM company is itself are called branded or IBM PC computer which are developed or assembled by other companies using the parts and principle of IBM PCs are called IBM compatibles. So, IBM compatibles are also called duplicate of IBM PCs.

  IBM PC	IBM Compatible
  1.   These computers are developed by IBM Company itself.	1.  These computer are developed by the companies other than IBM Company
  2.   These computer are also called branded or original PCs.	2.  These computer are generally called assembled or duplicate of PCs.
  3.   Generally Expensive	3.  Comparatively cheaper.
  4.   It is more reliable.	4.  It is less reliable.
  5.   These computer are reliable, durable and have better quality than IBM Compatible.	5. These computers are less reliable, less durable, have low quality.

   

  4) On the basis of Model:

  1) XT Computer:-

  XT (Extra technology) computer are the old technology computers with much slower processing speed (not more than 4.77 MHz.). Advanced GUI (Graphical user interface) based

  Software like (Windows) can’t be run in these computers. Everything was based on text based system.

  2) AT Computer:-

  AT (Advanced Technology) computers are the new technology computers. They are faster in processing (more than 2 GHZ) and can run any type of software whether that is text based or GUI based.

  3) PS/2 Computer:-

  PS (personal system)/2 computers actually, these are not totally different models of computers but are refinement of AT computers. These models were built 1990 and mostly used in laptop computers. Rechargeable and battery operated systems with faster and flexible.

   

  Measurement unit processing speed and storage unit

  Computer Speed

  A computer is a very fast device. Inside the system unit, operations occur through electronic circuits. When data, instructions and information flow along these circuits, they travel at the speed of light. It can perform a task in a minute that may take days if performed manually. A modern computer can execute millions of instructions in one second.

  Measurement Unit

  The memory of a computer is divided into section, or cells, that each holds an equal amount of data. Each of these cells contain one bit of information, i.e., each cell contains a 0 or a 1. The symbols 0 and 1 are together called binary digits or BITS. It is the smallest unit of information handled by a computer. A combination of bits is used to store instructions and data in the computer memory. They are called nibbles, bytes, words depending on the number of bits they have.

   

  Data Storage Units Chart: From Smallest to Largest

   

  Unit	Shortened	Capacity
  1 Bit	B	1 or 0 (on or off)
  1 Nibble	–	4 bits
  1 Byte	B	8 bits
  1 Kilobyte	KB	1024 bytes
  1 Megabyte	MB	1024 KB
  1 Gigabyte	GB	1024 MB
  1 Terabyte	TB	1024 GB
  1 Petabyte	PB	1024 TB
  1 Exabyte	EB	1024 PB
  1 Zettabyte	ZB	1024 EB
  1 Yottabyte	YB	1024 ZB

   

  MOBILE COMPUTING

  Mobile computing is the form of human-computer interaction by which a computer is expected to be transported during normal usages. Mobile computing has three aspects: mobile communication, mobile hardware and mobile software.

  The first aspect addresses communication issues in ad-hoc and infrastructure networks as well as communication properties, protocol, data format and concrete technologies. The second aspect is on hardware, e.g., mobile device or device components. The third aspect deals with the characteristics and requirements of mobile applications.

  Fig: Mobile Computing

  Mobile computing is a generic term describing one’s ability to use technology while moving, as opposed to portable which is the only particle for use while deployed in a stationary configuration. A mobile computing device is created using mobile components, such as mobile hardware and software.

  Mobile computing devices are portable devices capable of operating, executing, providing services and applications to a computing device. It is a computing device used in transit. Users can access data and information from wherever they are. Here’s the example view of how does the mobile computing works on a server and mobile networks.

  Fig: Working of Mobile Computing

  Mobile computing is the process of computation on a mobile device. In mobile computing, a set of distributed computing systems or service provider servers participate, connect, and synchronize through mobile communication protocols.

  Mobile computing provides decentralized (distributed) computations on diversified devices, systems, and networks, which are mobile, synchronized, and interconnected via mobile communication standards and protocols.

  Many types of mobile computers have been introduced since the 1990’s including wearable computer, PDA, enterprise digital assistant, smart phone, UMPC (Ultra-mobile PC), Tablet PC.

  CHARACTERISTICS OF MOBILE COMPUTING

  • It is a portable device that you can carry during mobility.
  • It has limited processing and storage capability.
  • It includes mobile communication, mobile hardware, and mobile software.
  • It usually contains touch screen for providing input.
  • It contains on-screen or virtual keyboard for proving text inputs. However, an external keyboard can be connected by using USB port, infrared or Bluetooth.
  • It contains the camera, speaker, and microphone etc.
  • It contains handwriting recognizing software.
  • Most of the mobile computing devices contain memory card slot to expand the storage capacity.
  • It has wireless connectivity such as Bluetooth, Wi-Fi, to connect the Internet or with other computing devices as well as the wired connection through the USB port.
  • The most mobile computing device can synchronize their data with the applications on a user’s computer.
  • It can be used for cloud computing and remote access.
  • It uses the mobile computing operating system such as Android, iOS, Windows Mobile OS, Plam OS.
  • It can include GPS (Global Positioning System) receiver for navigation.

  Fig: Mobile Computing

  1.2. Computer System and I/O devices

  Concept of Computer Architecture and Organization

   

  Computer architecture

  Computer architecture is a specification detailing how a set of software and hardware technology standards interact to form a computer system or platform. In short, computer architecture refers to how a computer system is designed and what technologies it is compatible with.

   

  • Computer Architecture is the conceptual design and fundamental operational structure of computer system.
  • It is the coordination of abstract levels of a processor under changing forces, involving design, measurement and evaluation.
  • It also includes the overall fundamental working principle of the internal logical structure of a computer system.
  • The computer architecture is the theory behind the design of a computer.
  • Computer Architecture sets the design requirement or specification of computer system.
  • It is the design of the task performing part of computers.
  • It is the science and art of selecting and interconnecting hardware components to create computer system.

  6. Application Layer	SOFTWARE LEVEL
  5. System Software Layer
  4. Machine Layer	HARDWARE LEVEL
  3. Micro Programmed Layer
  2. Digital Logic Layer
  1. Electrical and electronic component Layer

  Fig. Layers of computer Architecture

  1. Electrical and electronic component layer

              This layer is also referred as physical device layer,

  • Transistor
  • Capacitors
  • Registers
  • Diode
  • ICS etc.
  2. Digital Logic Layer

              All most basic operations of the machine are provided at this level. The basic elements at this level can store, manipulate & transmit data in the form of simple binary representations. These digital logic elements are called gates.

  3. Micro program Layer:-

  A sequence of micro instruction constitutes the micro program is called firmware. It is permanently stored in ROM.

  4. Machine Layer

  Several Hardware Levels are presented in machine level. These are the basic elements of computer.

  They are – processor, input/output devices,

  Main memory, Auxiliary memory, Translator

  Program (Compiler, Assembler, Interpreter).

  5. System Layer:-
  • System software control overall operation of the computer.
  • Functions Like
    • File editing, Storage Management, resource accounting, I/O Management, Database Management etc.
    • Example, MS-windows, Linux, Unix, Ms-DOS,

              Language Processor, Utility software.

  6. Application Layer:-
  • Application software is the software which is used to perform the specific task needed by the user.
  • Example, Auto CAD, MS-office Package, Adobe Photoshop, Tally etc.

   

  Computer Organization

  • Basic different parts are constructed and organized in a computer they are CPU, Memory, Input and output system that combination is called computer organization.
  • Computer organization refers to the operational units and their interconnection that realize the architecture specification. Computer organization deals with physical aspects of computer design, memory and their types and microprocessors design.
  • Whereas computer architecture deals with design aspects of computer that assembly programmer needs to know like instruction set (i.e. instruction supported), instruction format (i.e. how instruction will be specified), addressing modes, data types supported, etc.

                                                             

   

  Computer Architecture	Computer Organization
  Computer architecture is concerned with the structure and behavior of computer system as seen by the user.	Computer organization is concerned with the way the hardware components operate and the way they are connected together to form a computer system.
  It includes information, formats, instruction set, and techniques for addressing memory.	It includes Hardware details transparent to the programmer such as control signal and peripheral.
  It describes what the computer does.	It describes how the computer performs.Ex, circuit design, control signals, memory types and etc.

   

  Computer System

  A computer system refers to the fully function able system that is integration of both hardware and software. The hardware components of a computer of a computer system are physical components that are tangible such as keyboard, mouse, processor, mother board, main memory, secondary memory, monitor, printer, etc. whereas the software components are logical components that make physical component work such as data, information, computer instructions etc.

   

  The computer is a device that operated upon information or data. It is an electronic device which accepts inputs data, stores the data, does arithmetic and logic operations and provides the outputs in the desired format. The computer receives data, process it, produces output and stores it for further references. So, a computer should have at least four major components to perform these tasks. A block diagram of the basic computer organization has the following functional units.

  Computer system is the integration of main processing unit with the supporting chips or processors and the devices attached with it.
  – It is the combination of input unit, central processing unit and output unit.
  – Computer system is just like the system of our body.

   

   

   

   

   

   

  Component of computer System

   

  Fig: Block diagram of computer architecture

   

  1. Input unit: it accepts the data or instructions given by the user and it converts the data and instructions from man readable to machine readable code. Some common input devices are keyboard, mouse, scanner punched cards etc.

   

  1. Processor/CPU: CPU is the portion of a computer system that carries out the instructions of a computer program, and is the primary element carrying out the computer’s functions. Some of the primary components of a CPU are:
  2. Registers: These are the primary memory of computer system. They are mainly used to store data during the time of processing inside ALU. The registers within CPU are special purpose temporary storage locations.
  3. Control unit: The control unit is the brain of the CPU itself. It controls overall operations and devices of computer.
  • Arithmetic Logic Unit: ALU carries out the arithmetic and logical operations on the data made available to it.
  1. Primary/ Main Memory: It is a volatile memory of computer. As soon as a computer starts, primary memory stores all running applications, operating system, user interface and any others. Its storage capacity is smaller but faster.
  2. Secondary/ Auxiliary storage: It is the secondary memory of computer. They have slower access rates but greater storage capacity and data stability. Auxiliary memory holds programs and data for future use because it is non-volatile.
  3. Output Unit: When the computer its processing task, the results must be conveyed back to the user. Information from the CPU is converted into an understandable form through output devices.

  I/O (Input/Output)  devices

  Input Unit

  The input unit is formed by the input devices attached to the computer. Input devices are used to interact with a computer system or used enter data and instructions to the computer. These devices convert input data and instructions into a suitable binary form such as ASCII, which can be acceptable by the computer. In brief, an input unit performs the following function:

  • It accepts data and instruction from the outside worlds.
  • It converts these data and instruction into computer understandable from a binary form.
  • It supplied the converted data and instruction to the computer system for further processing.

  Example of input devices are keyboard, mouse, scanner etc.

  COMMONLY USED INPUT DEVICES

  • Keyboard

  A keyboard is the primary input device through which instructions and data are entered into the computer. It was first invented, in 1868 A.D, in America by Christopher Latham Sholes. This commonly used input device mostly uses a Qwerty layout. The layout is called “Qwerty layout” because such keyboard has those keys as the first 6 letters on top of an alphabetic line of a keyboard.
  
  

  Fig: Keyboard
  
  

  A keyboard is connected to the CPU with a cable. When a key is pressed, an electronic signal is produced which is then detected by an electronic circuit called keyboard encoder. The main function of an encoder is to detect which key has been pressed and to send a binary code that is correspondent to the pressed key of a computer. This binary code may be ASCII, EBDIC or HEX code.

  Earlier, keyboard with serial port containing 9 pins was in use. These days, we have USB (Universal Serial Bus) port keyboard and some even wireless. Keyboard with navigation keys like play, pause, next, previous, etc. with multimedia functions is also available. There are 4 types of keyboards for PCs now available. The first 3 were invented by IBM while, the latter is the result of changes made when Microsoft Windows 95 was released. They are:

  1. The 83-key keyboard (PC/XT)
  2. The 84-key keyboard (PC/AT)
  3. The 102-key keyboard (called the extended keyboard)
  4. The 105-key Microsoft Windows 95-compatible keyboard)
     
     
  • Mouse

  A mouse is a small input device which is used to point, draw and select items that are displayed on the computer screen. The pointer of the mouse is called a cursor. As we move the mouse across the screen, the cursor moves according to the movement of the mouse. It was invented in 1960 A.D by Douglas Englebart. 
  
  
  

  Fig:Mouse

  
  A mouse is one of the most important and popular input devices. Its movement and the direction of movement are detected by 2 rotating wheels on the underside of the mouse. These wheels have their axes at right angles where, in each wheel is connected to a shaft encoder which emits electrical pulses for everyday increment movement of the wheel. The pulses transmitted by the mouse determine the distance moved.

  There are 3 types of mouse found in a market.They are:

  a.) Scroll mouse: It is a type of mouse which comes with a scroll wheel perpendicular to its surface. This scroll wheel or a mouse wheel is made up of a rubbery disc or hard plastic on the computer mouse. It is generally located between the right and left mouse buttons.

  Fig: Scroll Mouse

  b.) Optical mouse: It is a more advanced mouse which uses a light source, typically LED (Light Emitting Diode), a DSP (Digital processing) and an optical sensor instead of the regular mouse ball. It uses a light detector such as an image sensor or an array of photodiodes to detect any relative movement to a surface.

  
  Fig: Optical Mouse

  c.) Laser mouse: It is an even more advanced mouse which uses laser to detect movements on a surface. It can track more than 2,000 DPI (Dots Per Inch) whereas, a typical optical mouse can track between 400 and 800 DPI only. This mouse emits light to the surface where it is put on. The emitted light is reflected back which tells the computer to control the pointer on the screen. Generally, laser mouse available nowadays is connected to the USB (Universal Serial Bus) port.

  Fig:Laser Mouse
  
  
  

   

   

  • Joystick

  The joystick was invented, in 1944 A.D., in Germany but the video game joystick was invented in, 1967 A.D. A joystick is a stick which is mounted on a spherical ball which moves in a socket. It allows the user to navigate easily around the display on the screen. A user may move the stick on the device in different directions. This is particularly useful at homes for playing video games and for indicating positions in graphic systems.

  Fig:Joystick
  
  

  • Touch Pad

  A touch pad is a small touch-sensitive pad that is used as a pointing device in portable computers. It can be used in place of an external mouse. It uses pressure sensors to track the position of a device on its surface. Each position on the touch pad is translated to the specific location on the screen.A touchpad is operated by using your finger.

  
  
  Fig:Touch Pad

   

  • Track Ball

  A track ball is an upside down of a roller mouse. It was used to be a basic input device in laptops earlier. It is similar to the mouse but with a mouse, the ball is rolled by moving the entire unit over the surface whereas, with track ball, the ball itself is rolled with fingers.

  
  Fig: Trackball

  • Scanner

  The scanner is an input device that needs images or text and converts the data into digital signals. The image is scanned and converted into a format that the PC can interpret. It was invented by Rudolph Hell, in 1963 A.D, in Germany.

  Fig: Scanner
  
  
  

  A scanner works by digitizing an image, dividing it into a grid of small dots called pixel and representing each dot with RGB value for that pixel value by binary bits. The resulting matrix of bits is called a bitmap, which can be stored in a file and can be displayed on a screen.

  • Bar Code Reader

  The Bar Code Reader is a device which is used to read a barcode field. Bar Code is a technology that uses white spaces and black bars to represent encoded information. This encoded information can be read with an optical device that converts the bars and spaces into an electrical signal which is then decoded into the original characters. The bar code was invented by Woodland.

  Fig: Barcode reader

  The bar code reader is used in labeling consumer products and books. It is detected as ten digits. The first 5 digits identify the supplier or manufacturer of the item whereas, the second 5 digits identify an individual product. The code also contains a check digit to ensure that the information read is correct.

  • Light Pen

  A light pen is a pencil shaped device which is used to select screen positions by detecting the light coming from points on a screen. It was 1^stinvented in 1952 A.D, in MIT (Massachusetts Institute of Technology). A light pen is sensitive to the short burst of light emitted from the phosphor coating at the instant the electron beam strikes on a particular point.

  
  Fig: Light pen

  Though the light pens are still in use, they are not as popular as they used to be as they have several disadvantages comparing to other input devices.

  • OCR (Optical Character Reader)

  Optical Character Reader (OCR) is the device that helps in the recognition of printed or written text characters by a computer. OCR is used for reading text from paper and translating it into a form that the computer can manipulate. An OCR reader scans the document using the photoelectric device to convert it into electric signals. These patterns are then compared with the stored patterns of the characters which the reader can recognize. If a match is found, the character scanned is identified otherwise, it is rejected by the reader. This device is widely used in airlines, banks, postal offices (for reading postal code), etc.

  
  Fig: Optical Character Reader

  • OMR (Optical Mark Reader)

  Optical Mark Reader is widely used device for scoring answers for multiple choice questions. It can sense the presence of a pen or pencil mark. Special marks such as squares or bubbles are prepared on examination answer sheets or questionnaires .The user fills in these squares or bubbles with soft pencil or ink to indicate their choice. These marks are detected by the Optical Mark Reader and the corresponding signals are sent to the processor.

  
  Fig: Optical Mark Reader

  • MICR (Magnetic Ink Character Reader)

  Magnetic Ink Character Reader has been used to read documents that are written by a special ink made of a magnetic material called magnetic ink. MICR is capable of reading characters on a paper written with the magnetic ink which is magnetized during the input process. The MICR reads the magnetic pattern of the written characters. To identify the characters, these patterns are compared with a special pattern stored in the memory. It is mostly used in banks and postal services.

  
  Fig: Magnetic Ink Character Reader

  • Touch Screen

  Touch screen is a kind of screen which is sensitive to user’s touch. One can use a finger to point the command or menu displayed on the screen. Touch screen was invented in 2009 A.D, in Apple store. It is widely popular on laptops.

  
  Fig: Touchscreen

  • QR Code Scanner

  It stands for Quick Response Code. The advanced form of Bar Code Reader is QR Code Scanner. A QR code is a pattern of black and white squares. The QR code of any product gives information about the website address. A QR code can be read and processed by a smartphone QR Code or a cell phone with the help of Apps or Applications.

   

  • Voice Input System

  The input system which is used to give the instruction to the computer invoice, without using the keyboard i.e. without typing is called Voice Input System. In Voice Input System, the speech is converted into electrical signals employing a microphone. The signals are sent to a processor for processing. Then, the signal pattern is compared with the pattern already stored in the memory .A word is recognized only when a choice is found, and then, the computer gives a corresponding output.

  
  Fig: Voice Input System

  A voice recognition system can be used in factories at places where both hands of workers are engaged in the job like if he is doing some handful of work and he wants to input some data into the computer. It can also be used to assist handicapped people or for identification purposes in banks, etc.

   

  Memory Unit

  This unit is also called storage unit. The data and instructions, which are entered through an input unit must be stored on the computer before the actual processing starts. The result produces by the computer after processing is also kept somewhere before passed to the output units. If intermediate results are produced during processing, it should be stored in somewhere in memory. The storage unit of a computer performs all these needs. In brief, the specific functions performed by the storage unit are as follow:

  • It stored data and instructions, which are entered through input devices.
  • It stores an intermediate result of processing.
  • It stores the final result of processing before these results are passed to an output device.

  The storage unit of computers consists of two types of memory or storage: primary and secondary storage:

  1. Primary / Main / Internal Storage

  Memory storage that communicates directly with CPU is called main memory. It enables the computer to store, at least temporarily data and instruction. It is mainly used to hold data and instructions and as well as the intermediate result of processing which the computer system is currently working on. Primary memory is volatile, that is, it lose its content when power supply is off. The Random access memory (RAM) is an example of a primary to main memory.

  Here are some of them that comes under the primary memory

  • RAM (Random Access Memory)

  Fig: Random Access Memory

  RAM is the read/write memory of the computer. It is used for both purpose read and write. It possesses random access property that means CPU can access any memory location in a random sequence form.

  It is a volatile memory. It stores data or information as long as power supply is on. But, after power supply is off, data will be gone. There are two types of RAM.

   

  Types of RAM

  • Static RAM (SRAM)

  SRAM stores data and programs as long as the computer is in ON state. It is expensive but faster for read/write than DRAM.it is typically used for CPU cache while DRAM is used for a computer’s main memory.

  Fig: Static RAM

  • Dynamic RAM (DRAM)

  The data stored in DRAM will be lost after a few milliseconds even if the computer is on. It is cheap but slow for read/write than SRAM.

  Fig: Dynamic RAM

  • Read Only Memory (ROM)

  ROM stands for Read only memory. It can be used only to perform the read operations. It does not have write access. It is non-volatile memory i.e, the information stored in it is permanent and is not lost even if the power supply is cut down.

  Fig: Read Only Memory

  It is used for permanent storage of programs. It is cheaper than RAM on per unit basis but while compared to storage ROM is expensive than RAM.

  Types of ROM

  • PROM (Programmable Read Only Memory)

  It is a programmable memory that users can write data at once only. The user can store permanent programs, data or any kind of information in PROM.

  Fig: Programmable Read only Memory

  • EEPROM ( Electrical erasable programmable read only memory)

  It is a memory that can also be erasable via electric. It can be erased and reprogrammed on the byte by byte basis single data or the entire chip can be erased.

  Fig: Electrical erasable programmable read only memory

  • EPROM ( Erasable Programmable Read Only Memory)

  It is an erasable memory. Data stored on it can be erasable via passing the Ultra-Violet light so that entire data will be erased.

  Fig: Erasable Programmable Read Only Memory

   

   

  Secondary / Auxiliary / External Storage

  Secondary memory is non-volatile and has a lower cost per bit. It generally has an operating speed far slower than that of primary memory. Secondary memory is also called as “Auxiliary Memory”. It is primarily used to store a large volume of data on the permanent basis that can be partially transferred to primary storage.

  Secondary storage is the storage device that is designed to store data and instructions (programs) in a computer relatively in permanent form. It is non-volatile storage.ie. Stored data and instructions can be retained even if the power supply is cut off. It is also known as backup memory. It is mainly used to transfer data to program from one computer to another computer. There is high capacity storage devices used to store data and program permanently. These are also used as backup devices which allows to store the valuable information as backup on which you are working on. The examples of secondary memory are Magnetic Disk, Optical disk, etc.

  Features of secondary memory

  1. It is not directly accessible to CPU;
  2. it requires primary memory for its operation.
  3. It is usually non-volatile memory.
  4. It is usually cheaper and slower for read /write operation than primary memory.

  Secondary memory is also called auxiliary memory or backup memory. These memories are used to store data and instructions permanently for future use. CD/DVD, pen drive, hard disk, etc. store data and instruction for future. The various types of secondary memory are Magnetic Tape, Hard disk, SSD (Solid State Drive), Optical Storage Disc, Pen drive, etc.

  1. Magnetic Storage

  Computer systems need to store data in digital format. One of the most widely used types of digital data storage is magnetic storage. This refers to any type of data storage using a magnetized medium. Several types of magnetized media are used in computer systems, including magnetic tape, floppy disks, Super disks, hard disks, etc.

   

  Magnetic Tape

  
  Magnetic Tape is a usable secondary storage device to store and retain a large volume of data. It is made up of a plastic strip of which one surface is coated with magnetic ink. Analog and digital data are stored in magnetic tape. Normally, minicomputer, mainframe computer, large scale business organization server, etc. uses magnetic tape for backup data and information. Magnetic tape driver are used to store and retrieve the data and information from magnetic tape. The main important function of magnetic tape is to store data safely for a long period of time.

  Magnetic Tape and Tape Drive

  Hard Disk

  Hard disk is commonly used storage device. It stores large amount of data and information permanently. It is also called fixed disk. It is made of aluminium materials and the surface is coated with the ferromagnetic element. Circular metal discs also called platters to rotate while writing or reading the data and information into them. It stores a large amount of data on hard disk. The speed of the hard disk is measured in rpm (revolutions per minute). The hard disks with 5400 rpm or 7200 rpm are generally used in present-day computer system.

  Hard disk capacity

  
  Hard disk must be formatted before use. There are thousands of track on the surface of hard disk. So, each track is divided into various sectors. Each sector stores 512 bytes. Header is used to read and write on hard disk. The storage capacity of hard disk is determined from number of disk or platter it contains and their density.

                                               Hard Disk                                  Track and Sector

  SSD (Solid State Drive)

  Hard disk can be replaced and upgraded by SSD (Solid State Drive) as new technology. Semiconductor chips are used to store data in SSD. The speed to read and write data is greater than hard disk. So its price is more expensive than hard disk. Laptop, notebook, ultra book, etc. uses SSD as storage device. Its storage capacity is about 4 TB but various companies are trying to develop SSD with high storage capacity. It is more costly than HDD (Hard Disk Drive).

  Solid State Drive

  Differences between SSD and Hard disk

  S.N.	Hard disk	SSD
  1	It is heavier than SSD.	It is lighter than hard disk.
  2	Its storage capacity is 500 GB to 100 TB.	Its storage capacity is 1 TB to 4 TB.
  3	It is cheaper than SSD.	It is more expensive than hard disk.
  4	It takes 6-7 watt electricity.	It takes 2-3 watt electricity.
  5	The file writing speed is 50-120 MB/S (megabyte per second)	The file writing speed is 200-550 MB/S (megabyte per second)
  6	It is made up of aluminium material.	It is made up of semiconductor microchip.

   

   

  External Hard Drive

  The working principle of hard disk is similar to that of internal hard drive but it is not placed inside CPU casing. It can be externally connected with a USB (Universal Serial Bus) port. It is portable and easy to carry. It is used to transfer data, information and software from one computer to another.

  External Hard Drive

  
  

  Pen drive

  Pen drive is a popular flash storage device. It is also called flash memory. It is connected through the USB ports. It is a small size and portable device. It can be carried in a pocket like pen. So it got its name as a pen drive. It is used to transfer data, information and software from one computer to another. It is made up of semiconductor chip which is EEPROM technology. The writing speed of pen drive of USB 3.0 is up to 60 MB/S and data reading speed up to 120 MB/S.

  Pen drive

  1. Optical Storage Disc

  The disc that uses laser light technology to store and retrieve data is called optical storage disc. The most commonly used optical storage discs are CD, DVD, Blu-ray disk, etc.

  CD (Compact Disc)

  In 1980, Philips Company of Netherland developed first CD or optical disk which was 12cm in diameter and had 72 minutes audio/video storage capacity. The laser ray technology is used to retrieve and store the data. The information on the optical disk is stored in the form of pits. The pits are tiny reflective bump.

  CD has the diameter of 12 cm. It’s weight is 18gm and width 1mm (millimetre). The data can be written on a CD only once. CD is made up of poly carbon and both surfaces are coated with aluminium. Nowadays, CDs are commonly used in microcomputer. It can be used to transfer data from one computer to another. The storage capacity of a CD is 700MB.

  The three types of optical storage devices are:

  • CD-ROM → Compact Disc – Read Only Memory
  • WORM → Write Once Read Many
  • CD-RW → Compact Disc – Rewritable
  1. CD-ROM stores data or programs like video, music, software, etc. for selling purpose developed by different company. The information stored on it is read-only.
  2. WORM is an optical storage media which is purchased as blank media and data can be written only once but can be read many times.
  3. CD-RW (Compact Disc – Rewritable) means read and write in it multiple time. It is similar to pen drive as information can be read from and written to the disk many times.

  CD (Compact Disk)

  DVD (Digital Versatile Disc)

  DVD stands for Digital Versatile Disc or Digital Video Disc. Its storage capacity is higher than CD. It stores multiple layers of data. The various DVD storage capacities are

  • Single Side Layer- 4.7 GB
  • Single Side Double Layer-8.5 GB
  • Double Layer Single Side- 9.4 GB
  • Double Layer Double Side-17.08 GB

  Philips, Sony, Toshiba/ Panasonic companies developed first DVD in 1995. DVD Drive is used to read/write the data on DVD.

   

   

  Differences between CD and DVD

  S.N.	CD	DVD
  1	Its storage capacity is 700MB.	Its storage capacity is up to 20GB.
  2	It is cheaper.	It is more expensive.
  3	It is used to store audio and software.	It is used to store video and software.
  4	Its types are CD-R, CD-RW, etc.	Its types are: DVD-RW, DVD+RW, etc.
  5	It was developed by Philips and Sony.	It was developed by Philips, Sony, Toshiba, Panasonic etc.

   

   

  Blue-ray Disc

  It is an optical data storage device. Its storage capacity is up to 200GB. It is mainly used to store high-quality audio and movie data. It is scratch resistant discs.

  5. Differences between Primary memory and Secondary memory:

  S.N.	Primary memory	Secondary memory
  1	It is also called main memory or internal memory.	It is also called auxiliary memory or backup memory.
  2	It is volatile and non-volatile memory.	It is non-volatile memory.
  3	The storage capacity is less.	The storage capacity is more.
  4	Its types are RAM, ROM, etc.	Its types are: Hard disk, CD/DVD, etc.
  5	It is made up of semiconductor.	It is made up of magnetic materials, poly carbon, etc.
  6	The data is directly accessed by the processing unit.	The data cannot be directly accessed by the processing unit.

   

  S.N.	Hard disk Drive-HDD	S.N.	Solid State Drive-SSD
  1	Its storage ranges 500 GB to 100 TB	1	Its storage ranges from 1 TB to 4 TB.
  2	It is cheap.	2	It is expensive
  3	It consumes more electricity. (6/7w)	3	It consumes very less electricity. (2/3w).
  4	It has rotating disk platters.	4	It does not have rotating disks.
  5	Produces sound while move.	5	It does not produce sound while working.
  6	R/W speed is 50-120 MB/s.	6	It is made of semiconductor memory chips.
  7	Platters are made of aluminum.	7	It is made of semiconductor Memory chips.

   

   

   

  Cache Memory

  Cache memory pronounced as cash, is a special high speed and expensive memory used in CPU, so that CPU doesn`t have to wait for data to be delivered. The most frequently used instructions are kept in the cache memory.

  Cache memory computer runs fast and smoothly. It doesn`t have to swap instruction in and out of RAM. Hence, the cache memory is placed in between CPU and RAM so that the speed of operation of main memory and cache memory together can meet speed requirements.

  Central Processing Unit (CPU) or Microprocessor

  CPU is the component that actually responsible for interpreting and executing most of the commands from the computer hardware and software and also controls the operation of all other components such as memory unit, input and output devices. It simply accepts binary data as input and processes data according to those instructions and provides the result as output. It is the logic machine. So, its main function is run the program by fetching instructions from the RAM, evaluating and executing them in sequence. In summary, the function of CPU or Microprocessor are as follow:

  • Read instruction from memory
  • Communicate with all peripherals using the system bus.
  • It controls the sequence of instructions.
  • It controls the flow of data from one component to another component.
  • Performs the computing task specified in the program.
  • Fetch-decode-execute.

   

  The CPU has three components responsible for different function, these components are Control units, arithmetic-logical unit (ALU) and Register.

  Fig: Components of CPU or Microprocessor

  Control Unit

  Control Unit is a part of the CPU that controls and coordinates activities of other units of computer system. It acts as a nervous system of computer. It controls the execution of instructions given to system. It coordinates the flow of data in or out of ALU, memory and various input or output devices.

  • It performs the data processing operations with the aid of program prepared by the user and send control signals to various parts of the computer system.
  • It gives commands to transfer data from the input devices to the memory to an arithmetic logic unit.
  • It also transfers the results from ALU to the memory and then to the output devices.
  • It stores a program in the memory.
  • It fetches the required instruction from the main storage and decode each instruction and hence execute them in sequence.

  Arithmetic Logic Unit

  Arithmetic logic unit is a part of CPU that can perform arithmetic operation like addition, subtraction, multiplication and division. Logical operation such as comparison AND, OR and Exclusive OR. It also performs logical comparison like equal to, greater than, less than, etc. to compare between two numbers.

  • It accepts operands from registers.
  • It performs arithmetic and logic operations.
  • It returns a result to register or a memory
  • The logical operations of ALU give the computer the decision-making ability.

  MU (Memory Unit- Register Array)

  Memory unit is also a part of CPU but not the part of main memory that store currently executing task. It is located inside the microprocessor and has very limited storage. It is used to store very active data and instructions temporarily during processing. Register are primarily used to store data temporarily during the execution of a program and are accessible to the user through instructions.

   

  BUS System

  • Bus refers to the path between the components of a computer. Actually bus is set of hardware line(conductor) which lies inside the computer through which data is transmitted from one part of computer to the another part.
  • The bus is a medium used to transfer data, memory address and control signal from one part to other part of computers.

  There are three types of bus which are described below:

  1. Address Bus: It is a group of wires or lines that are used to transfer the addresses of memory or I/O devices. It is unidirectional.
  2. Data Bus: It is used to transfer data within microprocessor and memory/input or output devices. It is bidirectional as microprocessor requires sending or receiving data.
  3. Control Bus: A control bus is a computer bus used by the CPU to communicate with devices that are contained within the computer. This occurs through physical connections such as cables or printed circuits.

  Virtual Memory

  • This is the hypothetical memory into the computer system. Exactly this is logical memory or not real memory exist into the computer system likewise physical memory (RAM).

  Create Virtual Memory

  RAM 128 MB

  Hard Disk 80 GB

  Input- 200 MB Data

  Fig.:- Mechanism of Create virtual Memory

  Memory that no longer physically exists within computer system is called virtual memory. Virtual memory is a technique that allows the execution of process that may not be completely in memory. Virtual memory automatically managers two levels of the memory hierarchy representing the main memory (RAM & ROM) and secondary storage (Hard disk). The operating system automatically manages the required space from secondary storage in the case of main memory is not sufficient to run particular program.

  Buffer

  Buffer is the temporary memory which stores the data from disk to RAM. The behavior of buffer is same as RAM but defined in disk.

  It is a temporary holding area for data; unlike register it stores more than one piece of data. It is normally used between the CPU and the input/output devices. The purpose of a buffer is to hold data prior being used by CPU.

   

  Buffer

  Card Reader

  CPU

  Printer

                                                                                      System Buffer

  Buffering is a process of utilizing temporary storage such as memory one a file for temporary purpose whereas fastest acting devices. Such as CPU can store data that can by slowly operating devices.

  • Buffer is a small, high speed memory
  • It can be a reserved section of RAM or can be located in the input/ output devices.
  • The technique which is used to keep both the CPU and input/output device busy all the time is called buffering.

   

  OUTPUT UNIT

  The output unit is formed by the output devices attached to the computer. Output devices are used to present result produced by the computer to the users. The output from the computer is in the form electric signals, which is then converted into human understandable form into human readable form.

  The examples of output devices are the monitor, printer and speaker.

  The main functions of the output unit are as follow:

  • Accepts the result produced by the computer which is in electric binary signals.
  • It then converts the result into human readable form.
  • Finally, it supplied the converted results to the outside word.

   

  Output devices

  A computer peripheral is a device that is connected to a computer but is not part of the core computer architecture.

  Softcopy

  Hardcopy

  Output Device

  The device which displays meaningful information from the computer is called an output device. So, an output is the result produced by processing unit. The common output devices are monitor and printer. Some other output devices are: plotter, speaker, headphone, etc. 

  Monitor

  Monitor is the most common output device. It is also called VDU (Visual Display Unit) in computer system. The output displayed on monitor’s screen in the form of text, videos and graphics is called soft copy output. On the basis of colour the monitors are of two types:

  1. Monochrome monitor and ii. Colour monitor

  Monochrome monitor

  The monitor which display output in one colour like green, white, black, blue, etc. is called monochrome monitor.

  Colour monitor

  The monitor which displays output in different colours more than sixteen is called colour monitor.

  The information displayed on the screen is made of combination of small tiny dots. The small tiny dots are called pixel.

  The clear screen consists of three terms as screen resolution, dot pitch and refreshes rate.

  1. Screen Resolution

  It represents the number of horizontal and vertical pixels. The clear screen is due to the high resolution of the monitor. The common resolution ranges are 640 ˟ 480, 1024˟768, 1600˟1200 etc. ii. Dot Pitch

  The dot pitch is a measure of how close the pixels or dots are to create an image on the monitor. So, it is measured in millimetre. The clear screen is due to the low dot pitch of the monitor.

  iii.      Refresh Rate

  The refresh rate is the rate due to each pixel on screen re-drawn. A low refresh rate results in a poor image on the screen. It is measured in hertz. So, the clear image is due to the high refresh rate.

  On the basis of technology, monitors are classified into three types as:

  1. CRT Monitor

  CRT stands for Cathode Ray Tube. It operates in the following ways:

  • The electron gun emits a beam of electrons cathode rays.
  • The electron beam passes through focusing and deflection systems that direct it towards specified positions on the phosphor-coated screen.
  • When the beam hits the screen, the phosphor emits a small spot of light at each position contacted by the electron beam.
  • It redraws the picture by directing the electron beam back over the same screen points quickly.
  
  

  CRT Monitor

  There are two ways Random scan and Raster scan by which we can display an object on to the screen.

  ii. LCD Monitor

  
  LCD stands for Liquid Crystal Display. It is very light, thin and consumes less power than CRT monitor. The two-layer in this monitor which consists of liquid crystal form an image. It is used in laptop, notebook, digital watch, desktop computer, etc. It is more expensive than CRT monitor and produces a high quality image on the screen. The fluorescent lamps are used for backlighting in LCD monitor for displaying image on the screen.

  LCD Monitor

  iii.       LED Monitor

  LED stands for Light Emitting Diode. It is very lighter and thinner than LCD and CRT monitors. It consumes less power than CRT and LCD monitors. Its working power is higher than others. So its lifetime is more and can be used for long-time-work. The quality of image on the screen is higher than that of other monitors. The diodes are used for backlighting in LED monitor for displaying the image on the screen. LCD and LED monitors are called flat panel displays.

  LED Monitor

  1. Printer

  Printer is a hard copy output device. It prints text & graphics on paper. There are many different types of printers available in market. Its speed is measured by CPS (Character per second), LPM (Line per minute) and PPM (Page per minute). The printers are classified in two types on the basis of printing quality. They are:

  • Impact printer
  • Non-impact printer

  Impact Printer

  An impact printer is a type of printer that operates by striking a metal or plastic head against an ink ribbon. Its structure is like a typewriter. It uses small pin-like objects or hammers that strike on the inked ribbon and characters are formed on the paper. These printers are slow and noisy. These printers use black or blue or red colour. The printing quality of impact printer is lower than non-impact printer.

  The three main types of impact printer are following:

       i.            Dot Matrix Printer

  Dot-matrix printer is a type of impact printer. The printer head contains a number of pins. The printer head strikes on the inked ribbon, the striking forms dotted characters on the paper. The speed of Dot-matrix printers ranges from 50 to 400 CPS (Character Per Second).

  Dot Matrix Printer

  1. Daisy Wheel Printer

  
  Daisy wheel printer is a type of impact printer. It uses hammer-like object to hit on the ink ribbon and a character is formed on the paper. The hammer contains letter face and is arranged in wheel like form and motor spins the wheel at a rapid rate. When desired characters spin to the correct position, a printer hammer strikes on the ribbon and output is formed on the paper. The speed of the daisy wheel printer ranges from 25 to 55 CPS (Character Per Second).

  Print Head of  Daisy Wheel

  • Line Printer

  Line printer is a type of impact printer. Its printing quality is better than that of Daisy wheel printer and Dot- matrix printer. It prints text line by line. So, it is called a line printer. The three types of line printer are:

  Drum printer: In this type, there is a cylindrical drum which continuously rotates over the paper surface and causes characters rise and hits on the ribbon.

  Chain Printer: In the chain printer, high-speed print chain is used. This chain contains different types of characters.

  Drum Printer

  Band Printer: In this line printer, steel print band is used to print one line printout on paper at a time.

  Non-Impact Printer

  The non-impact printer does not use the printing head to strike against ribbon and paper. Instead, small drops of ink are sprayed onto the paper. So non- impact printers are faster and are of high quality than impact printer. It does not produce sound while printing.

  Inkjet printer, laser printer, 3D printer are the popular types of non- impact printer.

  1. Ink-jet Printer

  Inkjet printer prints text and graphics on paper by spraying small drops of ink into paper. The speed of inkjet printer is generally 1 to 4 pages per minute. It uses an A4 size paper. The liquid colour-filled cartridge is used instead of ink ribbon. Colour inkjet printer uses black colour. Four colour-CMYK (Cyan, Magenta, Yellow, Black) cartridges are used for colour printout.

  Inkjet Printer

  1. Laser Printer

  A laser printer is a type of printer which makes use of a laser beam to produce an image on the drum or you can say that it is a printer that makes use of a focused beam of light to transfer text and images onto paper. It was first developed by Gary Starkweather at Xerox PARC in 1971. Laser printer makes use of laser technology for the printing of copies onto the paper. Its printout technology is like a photocopy machine. It uses colour powdered toner to print text and graphics on paper. Its printing quality is high.

  Laser Printer

  iii.       3D – Three Dimensional Printer

  
  Impact printer & non-impact printer prints text on paper but 3D printer prints an object. For example, any playing toys or any machinery parts are printed through the 3D printer. 3D printing builds parts out of plastic, metal and other materials directly from CAD (Computer-Aided Design) drawings that have been cross-sectioned into thousands of layers. This technology helps to build a 3D object by modelling. This technology is called additive manufacturing.

  3D Printer

  iii.      Graphic Plotter

  The graphic plotter is a hard copy output device which is used for good quality print or drawing like charts, map, engineering design, etc. Figures or maps are printed on graph paper placed on square board. The graphic plotter is used to print large size figure or map. It gets instruction from computer and draws a clear image by using pen. The different types of plotters are given below.

  Pen plotter: Pen plotter contains one or more pen. It prints colour drawing with shade.

  Electrostatic plotter: Electrostatic plotter does not contain any type of pen. It prints like laser printer.

  Dot-matrix plotter: Dot matrix plotter prints drawing like impact printer. Print head strikes on ink ribbon and prints images on paper.

  Graphic Plotter

  1. Speaker

  Speaker is a common audio output device. It is used to receive sound or music from computer system. It is used to covert digital data into audio analog data which user can understand. The quality of sound output depends on the speaker’s quality. For example, loud speakers, sub woofers, in- wall/ceiling speaker, outdoor speaker, etc. are the different types of speakers.

  Printer

  Different types of printers are described below:

  1. Dot matrix– printer: Dot matrix printer is an impact printer that produces text and graphics when tiny wire pins on the print head strike the ink ribbon. The print head runs back and forth on the paper like a typewriter. When the ink ribbon presses on the paper, it creates dots that form text and images.

   

  Advantages :

  1. Can print on multi-part forms or carbon copies.
  2. Low printing cost per page.
  • Reliable, durable.

   

  Disadvantages :

  1. Noisy.
  2. Limited print quality.
  • Low printing speed.
  1. Limited color printing.

   

  1. Inkjet printers: These are non-impact printers which print text and images by spraying tiny droplets of liquid ink onto paper. They are the most popular printers for home use.

   

  Advantages :

  1. Low cost.
  2. High quality of output, fine and smooth printing.
  • Good color printing
  1. Easy to use.
  2. Faster in processing

   

  Disadvantages :

  1. Print head is less durable.
  2. Expensive replacement ink cartridges.
  • Not good for high volume printing.
  1. Cannot use highlighter marker on inkjet printouts.

   

  1. Laser printers: Laser printers are non-impact printers which can print text and images in high speed and high quality resolution, ranging from 600 to 1200 dpi.

   

  Advantages :

  1. High resolution.
  2. High print speed.
  • No smearing.
  1. Cheap printing
  2. Good for high volume printing.

   

  Disadvantages :

  1. They are more expensive than inkjet printers.
  2. Except for high end machines, laser printers are less capable of printing vivid colors and high quality images such as photos.
  • They cost of toner replacement and drum replacement is high.
  1. Warm up time is needed.

   

  Hardware Interface

   

   

  Computer software

  Computer software is the collection of computer programs, procedures and documentation that performs different tasks on a computer system. The types of software are system software and application software. They are as follows:

  1. System software:
  2. Operating system: Windows, Mac, DOS, etc.
  3. Utility software: antivirus software, backup software, etc.
  • Language processor:
  1. Application software:
  2. Package software: word processing, database software, etc.
  3. Tailored software: JAVA, C++, etc.

   

  1. System software: It is software designed to operate the computer hardware to provide a platform for running application software it helps in running the computer hardware and the computer software.
  2. Operating system: It is the most important program that runs on a computer. Every general purpose computer must have an operating system to run other programs.
  3. Utility software: it helps to manage, maintain and control computer resources. Examples: virus scanning software, backup software, etc.
  • Language processor: it is a special type of computer system software that can use to translate the programs written in one language into another language.

   

  1. Application software: it enables the user to accomplish certain specific tasks. It can use to solve application type of problem.
  2. Package software: it is mainly designed by software companies to generalize the tasks. They are general purpose software. For examples: word processing software, database software, spreadsheet software, multimedia software, etc.
  3. Tailored software: it is specific purpose software. It is also called small type of software. These types of software are developed for specific tasks. They are written in high level languages.

   

   

Unit Wise Important Questions for Computer Science XI

Unit 2 Number System and Conversion Boolean Logic 

• What is a number system? What are the types of number systems used in a computer?
• What is the difference between positional and non-positional number systems?
• Define radix/base of a number system. What is the radix for binary, octal, decimal and hexadecimal number system?
• What is a binary number system? Why is it used in computer systems?
• What is hexadecimal number system?
• What is Boolean algebra? Give its applications.
• What is Boolean logic? Explain the three Boolean operators with the help of truth table.
• What is a truth table? Differentiate between NAND and NOR gate with truth table.
• What is a logic gate? Construct truth table, logic diagram, Venn diagram of AND, OR and NOT gates.
• Prove de-Morgan’s law with truth table.
• What is a Boolean law? Explain the different laws of Boolean algebra.
• State and verify the associative and distributive laws of Boolean algebra.
• Subtract 10001 from 11011 using 1’s and 2’s complement method.
• Convert the following as indicated.

1. (AF9)₁₆=(?)₂                b) (100101)₂=(?)₁₆             c) (129)₁₆=(?)₈     d) (2EA)₁₆= (?)₁₀

• Write Short notes on: a) Principle of Duality?                  b) Use of Boolean algebra

Unit 2 Number System and Conversion Boolean Logic

Computer Number System

The number system plays a vital role in computer calculations. Number system is an organized and systematic way of representing numbers. Number systems are basically of two types: non-positional and positional number systems.

1. Non-Positional Number System

The non-positional number system is a number system in which each symbol represents the same value, regardless of its position in the number. The symbols are simply added to find out the value of a particular number. The most common non-positional number system is the Roman Number System. It is a system of representing numbers devised by the ancient Romans. It is based on certain letters which are given values as numerals.

2. Positional Number System

Positional number system can be represented by a few symbols called digits, which represent different values depending on the position that they occupy. The value of each digit in such a number is determined by the digits itself, the position of the digit in the number, and by the base of the number system. The main positional number systems used in computer are decimal, binary, octal and hexadecimal.

Different types of number system are as follows:

1. Decimal number system: A number system having base or radix 10 is called decimal number system.

Examples: (789)₁₀ or (789)_D­

1. Binary number system: A number system having base or radix 2 is called binary number system.

Examples: (110)₂

1. Octal number system: A number system having base or radix 6 is called octal number system.

Examples: (1234)₈

1. Hexadecimal number system: A number system having base or radix 16 is called hexadecimal number system. Examples: (C01F)₁₆ or (C01F)_H

1. Decimal Number System

The base or radix of a number system is the number of different symbols available to represent any digit within that system. For example, the decimal system (Base 10) has a radix of 10. Decimal uses different combinations of 10 symbols to represent any value (i.e. 0, 1, 2, 3, 4, 5, 6, 7, 8, 9).

2. Binary Number System

A number system having base or radix 2 is called binary number system. It consists of 2 bits: 0 and 1. It is also known as Binary digits. It is specially used in internal processing of computer system.

An electronic circuit has two states either ON state or OFF state. The bit 1 represents the high voltage i.e. ON state and the bit 0 represents the low voltage i.e. OFF state of an electronic circuit. So it is used in computer system.

3. Octal Number System

A number system having base or radix 8 is called octal number system. It consists of 8 digits: 0, 1, 2, 3, 4, 5, 6, 7). It is also known as octonary number system. The octal system is used in computing as a simple means of expressing binary quantities.

4. Hexa- Decimal Number System

A number system having base or radix 16 is called hexadecimal number system. It consists of 16 digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F. It is also used in computer basically in memory management.

Number Conversion:

Rules

1. Decimal Number System to Others (Binary, Octal, Hexa-Decimal) Number System = Divide (2,8,16)
2. Others (Binary, Octal, Hexa-Decimal) Number System to Decimal Number System= Multiply (2,8,16)
3. Binary Number system to Octal Number system and Vice versa = 3 bit binary Grouping Method (421)
4. Binary Number System to Hexa-Decimal Number System and Vice versa= 4 bit binary Grouping Method ( 8421)
5. Octal Number System to Hexa-decimal Number System and Vice versa= 3 bit & 4 bit groping Method (421 & 8421)

Number Conversion examples

1. Decimal to Binary

Here, (149)₁₀

Therefore, (149)₁₀ = (10010101)₂

1. Decimal to Octal

Here, (804)₁₀

Therefore, (804)₁₀ = (1444)₈

1. Decimal to Hexa- decimal

Here, (1600)₁₀

Therefore, (1600)₁₀ = (640)₁₆

1. Binary to Decimal

Here, (100100)₂ = 2⁵ x 1 + 2⁴ x 0 + 2³ x 0 + 2² x 1 + 2¹ x 0 + 2⁰ x 0

= 32 + 0 + 0 + 4 + 0 + 0

= (36)₁₀

1. Octal to Decimal

Here, (2040)₈  = 8³ x 2 + 8² x 0 + 8¹ x 4 + 8⁰ x 0

= 1024 + 32

= (1056)₁₀

1. Hexa-decimal to Decimal

Here, (1E0D)₁₆ = 16³ x 1 + 16² x E + 16¹ x 0 + 16⁰ x D

= 4096 + 256 x 14 + 0 + 1 x 13

= 4096 + 3584 + 13

= (7693)₁₀

1. Binary to Octal

Here, (110111101)₂

Therefore, (110111101)₂ = (675)₈

1. Binary to Hexa-decimal

Here, (1001110111)₂

Therefore, (1001110111)₂ = (277)₁₆

1. Octal to Binary

Here, (375)₈

Therefore, (375)₈ = (11111101)₂

1. Hexa-decimal to Binary

Here, (ABC)₁₆

Therefore, (ABC)₁₆ = (101010111100)₂

1. Octal to Hexa-decimal

Here, (555)₈

= (101101101)₂

Therefore, (555)₈ = (16D)₁₆

1. Hexa-decimal to Octal

Here, (BCA)₁₆

= (101111001010)₁₆

Therefore, (BCA)₁₆ = (5712)₈

Fractional Number System Conversion

1. Decimal to Binary

Here, (0.55)₁₀

Therefore, (0.55)₁₀ = (0.100011)₂

1. Decimal to Octal

Here, (234.997)₁₀

Also

Therefore, (234.997)₁₀ = (352.776355)₂

1. Decimal to Hexa-decimal

Here, (689.336)₁₀

Also

Therefore, (689.336)₁₀ = (2B1.560418)₁₆

1. Binary to Decimal

Here, (101.1101)₂       = 2² x 1 + 2¹ x 0 + 2⁰ x 1 + 2^-1 x 1 + 2^-2 x 1 + 2^-3 x 0 + 2^-4 x 1

= 4 + 0 + 1 + 0.5 + 0.25 + 0 + 0.0625

= (5.8125)₁₀

1. Octal to Decimal

Here, (0.1042)₈           = 8^-1 x 1 + 8^-2 x 0 + 8^-3 x 4 + 8^-4 x 2

= 0.125 + 0 + 0.0078125 + 0.00048828125

= (0.1333)₁₀

1. Hexa-decimal to Decimal

Here, (FA.AEF)₁₆                 = 16¹ x 15 + 16⁰ x 10 + 16^-1 x 10 + 16^-2 x 14 + 16^-3 x 15

= 240 + 10 + 0.625 + 0.0546875 + 0.00366211

= 250.68335

1. Binary to Octal

Here, (101010.110111)₂

Therefore, (101010.110111)₂ = (52.67)₈

1. Binary to Hexa-decimal

Here, (10101.11011)₂

Therefore, (10101.11011)₂ = (15.D8)₁₆

1. Octal to Binary

Here, (77.226)₈

Therefore, (77.226)₈ = (111111.010010110)₂

1. Octal to Hexa-decimal

Here, (0.376)₈

= (011111110)₂

Therefore, (0.376)₈ = (0.7F)₁₆

1. Hexa-decimal to Binary

Here, (0.5AB)₁₆

                        Therefore, (0.5AB)₁₆ = (0.010110101011)₂

1. Hexa-decimal to Octal

Here, (0.226)₁₆

= (0.001000100110)₂

Therefore, (0.226)₁₆ = (0.1046)₈

 Binary Arithmetic

1. Binary Addition

Here, 11111 + 10001

Here, 1111 + 1111

1. Binary Subtraction

Here, 1100 – 11

Here, 101010 – 1001

1. Binary Multiplication

Here, 1010 x 1010

Here, 1111 x 1111

1. Binary Division

Here, 110100 / 110

Therefore, Quotient = 1000    and Remainder = 100

Here, 11010001 / 1001

Therefore, Quotient = 10111 and Remainder = 10

1’s and 2’s Binary Subtraction Method

A compliment is process of representing the negative numbers or bits in digital computer system. Complements are used in digital computers for simplifying the subtraction operation and for logical manipulation. Using complements, all the arithmetic operators can be performed in the form of addition.

The process of subtraction using 2’s complement is given below:

1. Make the number of digits equal in both minuend and subtrahend.
2. Calculate 2’s complement of subtrahend.
3. Calculate sum of minuend and 2’s complement of subtrahend.
4. Check the overflow digit (carry).

1. If there is overflow digit, discard it and the remaining bits would be final answer.
2. If there is no overflow bit then the result must be negative. So again, calculate 2’s complement of the sum and that would be the final answer.

1’S AND 2’S COMPLEMENT BINARY SUBTRACTION METHOD

1. Subtract 110 from 1101 using 1’s complement binary subtraction method.

Using 1’s complement method:

      Here    Main value= 1101

Second Value= 110

110. Make the number of bits equal as 1101 and 0110.
111. 1’s complement of second value 0110 is 1001.

• Add both the bits:

Here, we got overflow bit so discard it and add the remaining part.

0110 + 1 = 0111

Thus, 1101 – 110 = 111

Using 2’s complement method:

                  Here    Main value= 1101

Second Value= 110

110. Make the number of bits equal as 1101 and 0110.
111. 1’s complement of second value 0110 is 1001.

• 2’s Complement of 1001 + 1 = 1010.

1. Add both numbers:

Here, we got overflow bit which is discarded and the remaining part is our answer.

Thus, 1101 – 110 = 111

2. Subtract 1111 from 1100 using 1’s and 2’s complement binary subtraction method.

Here,  Main value =1100

          Second value= 1111

Both are equal digit.

Using 1’s complement method:

1. 1’s complement of second value 1111 is 0000.
2. Add both the bits:

Here, we did not get overflow bit so we again calculate 1’s complement of 1100 i.e. 0011 and put minus sign before it.

Thus, 1100 – 1111 = -11

Using 2’s complement method:

1. 1’s complement of second value 1111 is 0000.
2. 2’s complement of 0000 + 1 = 0001.

• Add both numbers:

Here, we did not get overflow bit so, we again calculate 2’s complement of 1101 and put minus sign before it.

i.e. 0010 + 1 =0011

Thus, 1101 – 110 = -11

9’S AND 10’S COMPLEMENT DECIMAL SUBTRACTION METHOD

1. Subtract 123 from 1234 using 9’s and 10’s decimal subtraction method.

Using 9’s complement method:

                         Main value=1234

                                    Second value=123

123. Making the numbers equal in both minuend and subtrahend as 1234 and 0123.
124. 9’s complement of 0123 is (9999-0123) = 9876.

• Adding both numbers:

Here, we got overflow digit, so we discard it and add it to the remaining part.

Thus, 1110 + 1 = 1111

Using 10’s complement method:

                        Main value=1234

                        Second value=123

123. Making the numbers equal in both minuend and subtrahend as 1234 and 0123.
124. 9’s complement of 0123 is (9999-0123) = 9876.

• 10’s complement of 0123 is (9876+1) = 9877.

1. Adding both numbers:

Here, we got overflow digit, so we discard it and remaining will the answer.

Thus, 1234 – 123 = 1111

2. Subtract 4567 from 567 using 9’s and 10’s decimal subtraction method.

Using 9’s complement method:

                        Main value= 567

                                    Second value= 4567

Using 9’s complement method:

4567. Making the numbers equal in both minuend and subtrahend as 0567 and 4567.
4568. 9’s complement of 4567 (9999-4567) is 5432.

• Adding both numbers:

Here, we did not get overflow digit, so we again calculate 9’s complement of it.

i.e. 9999-5999 becomes 4000

Thus, 567 – 4567 = 4000

Using 10’s complement method:

4567. Making the numbers equal in both minuend and subtrahend as 0567 and 4567.
4568. 9’s complement of 4567 (9999-4567) is 5432.

• 10’s complement of 4567 (5432+1) is 5433.

1. Adding both numbers:

Here, we did not get overflow digit, so we again calculate 10’s complement of it.

i.e. (9999-6000)= 3999 + 1 = 4000

Thus, 567 – 4567 = 4000

Boolean algebra

Boolean algebra:

Boolean algebra is a study of mathematical operations performed on certain variables (called binary variables) that can have only two values: true (represented by 1) or false (represented by 0).

Logic Function (Boolean Function):

A logic function is an expression algebraically with binary variables, logical operation symbols, parenthesis and equal sign, is known as Boolean function. Example, F= A.B.C’+A.B

Truth Table:

Truth table is a table which represents all the possible values of logical variables/statements along with all the possible results of the given combinations of values. For example, following logical statements can have only one of the two values (TRUE (YES) or FALSE (NO)).

Logic gates:

Logic gates perform basic logical functions and are the fundamental building blocks of digital integrated circuits. Most logic gates take an input of two binary values, and output a single value of a 1 or 0.

1. AND Gate: AND gate generates true output if all the inputs are true, otherwise it generates false output. It is denoted by (.) operator and graphically represented by:

Logical Symbol

Truth Table

2. OR Gate: OR gate generates true if at least any one of the input is true, otherwise it generates false

     Output. It is denoted by (+) operator and graphically represented by:

Logical Symbol

Truth Table

3. NOT Gate: It is also known as inverter. It inverts the input state from true to false and vice versa. It is denoted by (^­_) or (‘) operator and graphically represented by:

 Logical Symbol

Truth Table

4. NAND Gate: NAND gate is the combination of AND and NOT gate. NAND gate generates true (1) output if at least any of the input is false otherwise, it generates false output. Graphically it is represented by:

Logical Symbol

Truth table

5. NOR Gate: NOR gate is the combination of the OR gate and NOT gate. This electronic gate produces True (1) output when all inputs are False (0) otherwise the output will be False (0). It is the complement of the OR gate. It has two or more inputs and only one output.

Logical Symbol:

The truth-table of NOR gate is:

6. Exclusive (X-OR)Gates:

The XOR gate produces false output (0) when both the inputs are same otherwise, the output will be true (1). It can also have two or more inputs which produces only one output.

Logical Symbol:

The truth table of X-OR gate is given below:

7. Exclusive-NOR(X-NOR) Gate:

The XNOR (exclusive-NOR) gate is a combination XOR gate followed by an inverter. Its output is “true” if the inputs are the same and output is “false” if the inputs are different.

The X-NOR gate symbol is given below:

The truth table of X-NOR gate is given below:

There are 2 De Morgan’s laws or theorems:

1. Theorem 1: The complement of a sum of variables is equal to the product of the complement of each variables.

(A+B)’ = A’.B’

Here, (A+B)’ = A’.B’ thus proved.

1. Theorem 2: The complement of a product of variables is equal to the sum of the complement of each variables.

(A.B)’ = A’ + B’

Here, (A.B)’ = A’ + B’ thus proved.

Duality principle:

Duality principle state can be obtained by replacing AND (.) with OR (+) and vice versa, 1 with 0 and vice versa keeping variables and complements and variables are unchanged.

For example, duality of the expression A.B’ = A+B’ and A’.B+C = A’+B.C

Laws of Boolean algebra

The Boolean laws are the rules for manipulating Boolean variables by using Boolean operations. This set of rules states that how variables and values assigned with the Boolean operators reacts. These laws are used to circuit minimization. The process of shorting the length and using minimum components to construct same functioning circuit is called circuit minimization. The Boolean laws are as follows.

7.

a.

Here, A.(B +C) = A+(B.C)

b.

Here, A.B + C.1 + 0.1 = A + B.C + 0.1 + 0

c.

Here, C.D + A.0 + 1 = C + D.A + 1.0

d.

Here, 1.0 + A + C.1 = 0 + 1.A.C + 0

8.

Associative law states that when ORing or ANDing more than two variables, the result is the same regardless of the grouping of the variables.

(a) (A + B) + C = A + (B + C)

(b) (A B) C = A (B C)

Proof:

Here, (A + B) + C = A + (B + C) thus proved.

Distributive law states that ORing/ANDing two or more variables and then ANDing/ORing the result with a single variable is equivalent to ANDing/ORing the single variable with each of the two or more variables and then ORing/ANDing the products/sums.

(a) A (B + C) = A.B + A . C

(b) A + (B . C) = (A + B) . (A + C)

Proof:

Here, A.(B+C) = A.B + A.C thus proved.

9.

a.

Here,

AB + A’BC + BC

= AB + BC(A’+1)

=AB + BC

=B(A + C)

The truth table is:

b.

Here,

PQ’ + Q(P + Q) + P(P’ + Q)

= PQ’ + PQ + QQ + PP’ + PQ

= PQ’ + PQ + Q + 0

= P(Q’+Q) + Q

= P + Q

The truth table is:

c.

Here,

(X + Y)(XY’Z + XYZ + XY’Z’)

= XY’Z + XYZ + XY’Z’ + XYY’Z + XYZ + XYY’Z’

= XY’Z + XYZ + XY’Z’ + 0 + 0

=XY’ (Z + Z’) + XYZ

= XY’ + XYZ

= X(Y’+YZ)

= X(Y’+ Z)

The truth table is:

10.

Here,

a = A.B.C

b = A’ + B + C

c = A’.B’.C

Now, a + b + c = A.B.C + A’+ B + C + A’.B’.C

= B + A’ + C + A’B’C

= A’ + B’ + C

Principle of duality

• Changing to symbol OR (+) operation from AND (.) operation or AND (.) operation from OR (+) operation and digits 0 and 1 that is called principle of duality.
• Example, (x+y).z=(x.y)+z

Uses of gates

• All the gates are used to design digital electronic circuit.
• XOR and XNOR gates are used for circuit minimization.
• The NAND and NOR gates are used for construction of flash memory. Flash memories are used in various devices like PDA, Laptops, mobiles phones etc.
• Flash memory are constructed by using NOR are gates and external memories constructor by using NAND gates. For example, mini SD, Micro SD, Memory Cards.

Uses of Boolean algebra in computer science

• Logical function are useful not only to the hardware designer in implementing circuits but also to software designer in making decision, performing arithmetic, recognizing characters and patterns, checking for errors, formatting output and assembling and disassembling data.

Unit Wise Important Questions for Computer Science XI

Unit -3- Computer Software and Operating Systestem

1. What is an operating system? Explain the functions of operating system.
2. What is an operating system? Explain the different types of operating system with examples.
3. Differentiate between Application software and system software.
4. What do you understand by computer software? explain
5. What are the two types of computer software? Explain
6. What is system software? Name the different types of system software.
7. What is an operating system? What are the major functions of an operating system?
8. What is utility program? Name any two utility programs. Define them
9. What is tailored software? Give a few examples of such software.
10. What is packaged software? Give examples of packaged software.
11. Define operating system? Differentiate between CUI and GUI with examples.
12. Describe terms spooling and buffering.
13. Different between online processing and Real time processing.
14. Differentiate between Multiprogramming and Multiprocessing.

15. Write short notes on: a) Booting                         b) Linux   and Unix                             c) windows operating System
16. d) Time sharing OS   f) Open source software           g) Single user and Multiuser os       h) Types of Mobile OS

Unit 3- Computer Software and Operating System

3.1 Concept of Software

Computer program is a group of instructions given to the computer to perform a certain task. A program is used to solve a problem in computers. The program is written using a series of instruction that consists of all symbols, characters and certain rules.

Software consist series of instruction and decision rules that instruct the computer in executing a given task. Software is also called a computer program. It is a written by a using a programming language. It refers to a program or a set of instructions and applications used to manage and control various functions of a device such as a computer.

• It is a group of command that tells the computer what to do and how to do.
• It is the interface between the computer and the user. Without software a computer cannot do anything like a dead machine.

Types of Software

1. System Software
2. Operating System
3. Translating Program

                        iii. Utility software or system support program

1. Device Driver Software
2. Application Software
3. Customized or Tailored Software
4. Packaged Software or General Software

System Software

• The software which is designed operate, control and manage the actual operation of computer hardware is called system software.
• It is designed to provide a platform to run application software and operate the computer hardware.
• It is a collection of operating system, servers, device drivers, utilities and windows systems which helps in running the computer hardware and the computer system.
• The system software controls internal computer operation like reading data from input devices, sending, processed information to the device, checking system component, converting data and instruction to computer understandable (binary) form etc.

1. Operating System

• It is a program which act as an interface between the user, application program & hardware.

Without OS, We cannot start the computer & run other programs.

• It controls the execution of computer program like scheduling, debugging, input output control, compilation, storage & management of data etc.
• Some of its examples are Windows2000, Windows95/98, DOS, UNIX, Mac OS, etc.
• Below are some of its functions.
  • Provide security and backup.
  • Booting computers.
  • Controlling peripheral devices such as a keyboard, disk drives, printers, etc.
  • Provide interface between software and hardware.
  • Scheduling processes.
  • Memory management.
  • Keeping track of files and directories on the disk.
  • Recognize input from the keyboard.
  • Send output to the display screen.

2. Translating Program or Language Processor

It is a special kind of computer software which translates the programs written in one language into another language. It is compulsory for both low and high-level language. The types of language translators are:

1. Compiler
2. Interpreter

• Assembler

Translating program is used transfer instruction written in human understandable or readable language like VB, C, ASP.net, Java etc. to machine language which the computer understand.

3. Utility Software

Utility software (also known as service program, service routine, tool or utility routine) is computer software designed to help manage and tune the computer hardware, operating system or applications software by performing a single task or a small range of tasks.

Examples are Disk fragmentation, Disk Cleanup, Backup & Recovery, Antivirus, File managers, Data compression etc.

• Disk defragmenters rearranges the fragmented files back together to improve file retrieval speed and efficiency.
• Disk check or scandisk is a free utility that can help you scan your disk drives for errors and fix them. It can also scan entire disk for bad sectors and try to recover them.
• Backup utility is a program that allows you to back up selected files or an entire disk to a removable storage medium.
• Antivirus software is a program or set of programs that are designed to prevent, search for, detect, and remove software viruses, and other malicious software like worms, Trojans, adware, and more.
• Disk cleanup (cleanmgr.exe) is a computer maintenance utility included in Microsoft Windows designed to free up disk space on a computer’s hard drive.
• Disk partitioning is the creation of one or more regions on a hard disk or other secondary storage, so that an operating system can manage information in each region separately.
• Disk compression is software designed to organize or compress data to maximize free disk space.
• File manager File manager or file browser is a computer program that provides a user interface to manage files and folders.
• Debuggers: These are used mainly to solve programming errors.

4. Device Driver Software

It is a system software that controls a particular type of device attached to a computer. It enables the operation of numerous devices, including mouse, keyboard printer, video card and CD-ROM drive by translating commands from the operating system or the user into commands understood by the associated component.

It also translates responses from the component back to the operating system, software application or user.

Application Software

• It is designed to do only specific task is called application software.
• The application software made for one purpose cannot do other task.
• Examples, Word processing, Inventory control, financial accounting, Result preparation, Reservation etc.

1. Tailored or Customized Software

• The software which is designed to meet the specific requirement of a particular person or an organization is called Tailored Software.
• It is written according to the demand of person or and organization.
• The tailored made for one organization cannot be used in another organization.
• Examples, Payroll system, sales ledger, Salary sheet, School Management System, Library System, banking software, hotel reservation software, hospital software, billing software, etc.

2. Packaged Software or General Software

• The software which is design to meet the common requirement of different people & organization. It is not possible to design software to fulfill the requirement of each of them.
• It is also called universal software.
• It should be user friendly.
• It should have menu driven facility.
• It should be designed for general purpose.
• Examples, Word processing Software, Database Software, Spreadsheet Software, Multimedia Software, Presentation Software, MS-office (word, excel, PowerPoint etc.), Adobe Photoshop etc.

Web Based Software

Web best software is application software that is accessed over a network connection using HTTP rather than existing within device memory. Web based application often run inside a web browser. However web based application also may be client based, where a small part of the program is downloaded to a user’s desktop but processing is done over the internet on an external server. Web application are also known as web apps.

It includes light application like flash games online calculators, calendars, web based email and so on as well as more intensive applications such as web based word processor and spreadsheet application like (Google doc and Google spreadsheet).

Mobile Application

Mobile application (mobile app is short) is a software application developed specifically for use on small, wireless computing devices such as smartphones and tablets.

It execute when we press an icon on the mobile device such as an iPad or Android phone. The mobile application usually fall into three basic categories.

1. Native: Mobile application that runs only on the specific hardware for which it is designed.
2. Web based a mobile application that runs makes use of the internet connectivity to provide some or all of its functionality.
3. Hybrid: A combination of native and web based apps.

Features of Mobile Application

• Faster access speed
• Instant online and offline access
• Push notification and instant updates
• Interactive engagement

Different between Application and Software.

3.2 Concept of Operating

Operating system is a computer program (a system software) that acts as intermediate between the user and computer hardware. On other word operating system is an organized set or collection of software program that control the overall operation of the computer system.

Fig. interface between the user & computer hardware

As computer consist of various resources (parts) like memory, CPU, disk etc. it’s very difficult for the user computer to understand how to operate them directly. So operating system became interprets between the computer hardware and user.

OS is a resources manager which is used to operate the computer properly by managing following.

–  Memory Management                    – I/O Mgmt.

– Process Management                      – Error prompt Mgmt.

– File Management                             – Data & programs Mgmt.

Operating system is the master software to the computer. Without operating system computer is a like death machine (Ideal) so that it controls the overall parts of computer and force. It’s to function like a working computer. During starting to the computer operating system can control and handed overall function like memory management, CPU management. Input output device management etc. Therefore operating system like a soul of human being.

Objectives of Operating System

 An operating system is the master controller and sets the standard for all application software that a computer runs. It works like an air traffic controller to coordinate the activities within the computer. It performs a variety of important functions. Some of the important objectives of operating system are listed below:

• To make the computer system convenient to use in an efficient manner.
• To hide the details of the hardware resources from the users.
• To provide users a convenient interface to use the computer system.
• To act as an intermediary between the hardware and its users, making it easier for the users to access and use other resources.
• To manage the resources of a computer system.
• To keep track of who is using which resource, granting resource requests, and mediating conflicting requests from different programs and users.
• To provide efficient and fair sharing of resources among users and programs.
• Production of dumps, traces, error message and other debugging, detection aids.
• Accounting, maintenance of internal time clock and log of system and computer operators.

Role of operating system

Resource allocation:

The computer has many resources (hardware and software) which may be required to manage CPU time, Memory device, file, input, output device etc.

The OS act as a manager of these resources and allocates resources as required.

Control Computer system

OS control the execution of user program to prevent error and improper use of the computer.

User interfaces:

Os interfaces between user and computer resources. The user may be person or application like virus, messenger, MS-word. User interface provided easy way to run commands, copying file, deleting file, installing application program etc.

The function of Operating System

1. Memory Management functions

• Keeps track of memory by recording which is in use by which program and which is free.
• Decides which jobs should get memory and for how much time in case of multiprogramming.
• Allocates the memory space to a job.
• After the use of memory, makes it available for use by others.

2. Processor Management Functions

• Keep track of the processor by recording whether it is busy and if so who is using it.
• Decides which job should the processor use and for how long.
• Allocates the processor to the job decided.
• De-allocates the processor after use for an allotted time.

3. Device Management Functions

• Keeps track of I/O device and channels. i.e., which devices is in use and by which job.
• Decides which job should use the device and for how long.
• Allocate the device to the job.
• De-allocates the device after use.

4. Program and Data Management

• Keeps track of files, i.e., which files are in use and by which jobs and also maintain a directory of files.
• Decides which job should use the files and for what purpose, i.e., read/write/execute.
• Allocates the file for use.
• De-allocates the file, i.e., close the file.

5. File or Storage Management

Disk storage is only one of the memory types that must be managed by the operating system, and is the slowest. The different types of memory to be managed in a computer system are given here in the order of their speed, the fastest memory first.

6. I/O Management

Input/output (IO) is an essential element for the operation of any computer. It allows the computer to interact with peripheral devices such as a keyboard, mouse, terminals (like modem, TV card, and NIC card), disks or tapes (CD, DVD, and Floppy disk), printer etc.

Other Important Activities

• Security− By means of password and similar other techniques, it prevents unauthorized access to programs and data.
• Control over system performance− Recording delays between request for a service and response from the system.
• Job accounting− Keeping track of time and resources used by various jobs and users.
• Error detecting aids− Production of dumps, traces, error messages, and other debugging and error detecting aids.
• Coordination between other software and users− Coordination and assignment of compilers, interpreters, assemblers and other software to the various users of the computer systems.
• Deadlock Prevention

A deadlock happens in operating system when two or more processes need some resource to complete their execution that is held by the other process.

• In the above diagram, the process 1 has resource 1 and needs to acquire resource 2. Similarly process 2 has resource 2 and needs to acquire resource 1. Process 1 and process 2 are in deadlock as each of them needs the other’s resource to complete their execution but neither of them is willing to relinquish their resources.

Deadlock prevention: OS ensures that the above condition does not hold, and thus prevents it from deadlock. It takes suitable action by the careful allocation of resources so that deadlock can be avoided. If deadlock cannot be avoided. OS detects it and tries to recover from it.

Interrupt handling: Interrupt is an event that alters the sequence in which the processor executes instructions.

Types of Interrupt

1. Hardware Interrupt: Interrupt generated by hardware devices such as keyboard, printer or chips on the system board is called hardware interrupt.
2. Software Interrupt: Interrupt signals generated or caused by programs or software are called software interrupts.

Operating System Terminology (Types of operating System)

1. Classification of OS based on the Processing Method:

1. Batch Processing OS
2. Real time system
3. Multiprogramming
4. Multiprocessing
5. Multitasking
6. Multithreading
7. Online Processing
8. Time Sharing
9. Network and Distributed

1. Batch processing OS:

   Batch processing operating system allowed to run only one program at a time. Batch processing operating system works on a series of programs which are held in a queue. The jobs with similar requirement were batched (grouped) together and run as a group is called batch processing.

— Example: MVS, MVS/ESA

   A batch system is one in which jobs are bundled together with the instructions necessary to allow them to be processed without intervention.

1. Multiprogramming:

   Multiprogramming allows execution of two or more programs in a main memory of the computer. In this environment, processor processes several programs simultaneously.

   A multiprogramming technique is used in the multi-user environment. It is the technique in which multiple users programs are executed simultaneously by single processor or CPU.

   Multiprogramming means when two or more programs are provided to the CPU for processing or loaded into the internal storage of CPU at the same instant.

1. Multitasking:

   A multitasking OS allows more than one program to run concurrently mainly in a single user system. Multitasking computers are capable of running several tasks or programs at the same time. For executing several tasks, it can be single or multiprocessing system. Examples, Microsoft Windows 2000, IBM’s OS/390, and Linux

1. Multiprocessing:

   An operating system capable of supporting and utilizing more than one computer processor. Linux, Unix, Windows OS are some example of multitasking operating system.

   Multiprocessing refers to a computer system’s ability to support more than one process (program) at the same time. MVS and UNIX are the two example.

1. Multithreading:

   Threads are individual processes that execute simultaneously in multi-tasking OS. The programmer must carefully design the program in such a way that all threads can execute at the same time without interfering with each other. Each processor can handle different tasks or different threads of execution for a single task and more processors can be added as necessary.

1. Time sharing management:

   It is a kind of multiprogramming OS which operates in an interactive mode with quick response time. The user request to the computer and get response on the user terminal. Hence this operating system is also called Online Operating System. A time sharing system allows the many users to simultaneously share the computer resources. Example CP/CMS.

   In this system, the CPU executes multiple jobs by switching among them, but the witches occur so frequently that the users can interact with each program while it is running.

1. Real time system:

   Real time operating system is method which controls environment by receiving data, processing them and taking action quickly at that time. Application of Real time system Operating system.

            — Rocket launching

            — Monitoring and controlling nuclear power station

            — Robotics                   — Traffic light control              — Airlines reservation

   It is an OS where there are a number of possibly unrelated external activities needed to be controlled by a single processor system. In such systems a hierarchical interrupt system was coupled with process prioritization to ensure that key activities were given a greater share of available process time. Examples: Basic real time monitor, BSO/RTOS, RT Linux, etc.

• Network and distributed system:

— Network operating system works under client/ server principle. The server provides services such as mail, database, printing etc. client computer take service provided by the server.

— When computers in a group work in cooperation, they make a distributed system. Distributed systems use multiple central processors to serve multiple real time application and multiple users. Data processing jobs are distributed among the processors accordingly to which one can perform each job most efficiently.

   Examples of network operating systems are Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, Novell NetWare, and BSD.

1. On-line processing:

   It is a fast processing in which input device is directly connected to computer. In this system, data transaction is available immediately. So, computers operations are carried on promptly as the event occurs. Example: ATM, Reservation system of buses, airlines, etc.

Classification of OS based on the User Interface

CUI (Character User Interface) / CLI (Command Line Interface) / TBI (Text Base Interface)

 In CUI , where the user provides the input by typing a commands string with the computer keyboard and the system provide output by printing text on the computer monitor. So, the commands are accepted and executed by a part of the OS called CUI.

Features of CUI

 —  CUI is more textual and less user friendly.

—  User have to remember syntax and commands.

—  It needs less amount of memory space.

—  It does not contain different components such as text box, icon, desktop, pointing devices etc.

—  CUI is faster than GUI.

—  Other peripherals like mouse, light pen and joystick are not recognized.

—  It cannot display graphics, pictures or icon.

—  It does not support multimedia environment.

—  It does not support multitasking, multiprogramming, multiprogramming etc.

GUI (Graphical User Interface)

A graphical user interface allows a user to enter commands by pointing and clicking at objects that appear on the screen. It takes advantage of the computer`s graphical capabilities to make the program easier to use for the users.

Features of GUI

— GUI is graphical and user friendly.

— Users don’t have to remember syntax and commands

— It needs large amount of memory space.

— It runs other windows based programs like Ms-word etc.

— It provide utility software to improve the functionality of the computer.

— It consists of different components such as text box, icon, desktop, pointing devices etc.

— It needs faster processor to operate.

— In GUI, other peripherals like mouse, light pen, joystick can be used.

— It supports multimedia environment.

— It supports multitasking, multiprogramming, multithreading etc

Classification of OS based on Mode of user

Single User

It allows one user at a time. Normally, only allows one user program to be run and processed at a time. It based on small microcomputer which allows a single user to operate the machine. Example are MS-DOS, PC-DOS etc.

Multiuser

It allows two or more users to run program at the same time. Some OS permit hundreds or even thousands of concurrent users. The OS systems of mainframe and minicomputers are multiuser systems. Examples are UNIX, LINUX etc.

Popular Operating Systems for Computing Systems

Personal computers have come a long way in a relatively short time, and much of the progress is due to the continuing advancements in operating system technologies. The evolution in operating systems has made personal computers easier to use and understand. There are a variety of operating systems in use today. Each has its own merits and demerits. The most popular operating systems used in personal computers are explained below:

Microsoft Disk Operating System

Microsoft Disk Operating System (MS-DOS) was developed by Microsoft. It is a single-tasking, single-user operating system with a command-line interface. It provides many capabilities that include efficient use of disk space, easy recovery facilities, high speed input/output operations and user-friendly command language.

Microsoft Windows

Microsoft Windows, or simply Windows, is a meta family of graphical operating systems developed, marketed, and sold by Microsoft. It is the most flexible and powerful operating system that makes computing on personal computers simpler than before. It includes support for networking, Plug and Play technology, longer filenames and Internet access.

Mac OS

The Macintosh Operating System (Mac OS) is an operating system (OS) designed by Apple Inc. to be installed and operated on the Apple Macintosh series of computers. Introduced in 1984, it is a graphical user interface (GUI) based OS that has since been released as multiple different versions.

Linux

Linux open source operating system, or Linux OS, is a freely distributable, cross-platform operating system based on Unix that can be installed on PCs, laptops, netbooks, mobile and tablet devices, video game consoles, servers, supercomputers and more. Popular Linux OS distributions include Debian, Ubuntu, Fedora, Red Hat and openSUSE.

Popular Operating Systems for Mobile Devices

A mobile operating system, also called a mobile OS, is an operating system that is specifically designed to run on mobile devices such as mobile phones, smartphones, PDAs, tablet computers and other handheld devices. The mobile operating system is the software platform on top of which other programs, called application programs, can run on mobile devices. Examples of mobile device operating systems include Apple iOS, Google Android, BlackBerry OS and Windows Phone.

Android

Android is the name of the mobile operating system owned by American company, Google. The OS is based on Linux, making it an open source. It most commonly comes installed on a variety of smartphones and tablets from a host of manufacturers offering users access to Google’s own services like Search, YouTube, Maps, Gmail and more.

Apple iOS

iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers mobile devices, including the iPhone, iPad, and iPod Touch. Users can only download apps for their Apple devices from the App store in iTunes. The Apple website indicates that more than 500,000 apps and games are available in iTunes for Apple devices.

BlackBerry OS

BlackBerry OS is a proprietary mobile operating system designed specifically for Research In Motion’s (RIM) BlackBerry devices. The BlackBerry OS is designed for smartphone environments and is best known for its robust support for push Internet email. The operating system provides multitasking. The BlackBerry OS runs on Blackberry variant phones like the BlackBerry Bold, Curve, Pearl and Storm series.

Windows Phone

Windows Phone is a family of mobile operating systems developed by Microsoft for smart phones. Windows Phone features a new user interface derived from Metro design language. It was first launched in October 2010 with Windows Phone 7. Windows Phone 8.1 is the latest public release of the operating system, released to manufacturing on April 14, 2014.

Cloud Operating System

A cloud operating system is a type of operating system designed to operate within cloud computing and virtualized environments. A cloud operating system manages the operation, execution and processes of virtual machines, virtual servers and virtual infrastructure, as well as the back-end hardware and software resources. It is designed for Netbooks, Mobile Internet Devices, and PCs that are mainly used to browse the Internet. A cloud operating system may also be called a virtual operating system

3.3 Windows Operating System

Microsoft Windows Environment

Microsoft Windows is the most common operating system for PCs. It provides the communication link between the computer hardware and software. It provides users with a graphical user interface (GUI) which allows them to manipulate small pictures called icons on the computer screen to issue commands. It is an extension of and replacement for Microsoft’s Disk Operating System.

Booting

It is the process of loading the system files of operating system in the memory of computer is called booting.

1. Cold Booting: When the computer is at off state and the user puts on the power switch on the computer, the computer read s it RAM space and searches for system files of DOS from disk drive.
2. 2. Warm booting: When the user is working with the computer and wishes to reboot the computer, i.e. press CTRL+ALT+DEL key at the same time.

Desktop:

The desktop is the background displayed on your computer screen. It is the total visible area on the screen which users get immediately after turning on the computer. Files, folders, and program icons can be displayed on the desktop for easy access to users.

Figure: Desktop

On the desktop, files, folders and programs are displayed on window frame. The desktop may contain many items such as Computer, Network, Recycle Bin, User, etc. The desktop can be customized with themes and backgrounds to personalize the look of the computer.

Start Menu:

The start menu provides access to the most useful items on your computer including all programs, most recent documents, help and support and other items on your computer. This menu appears by clicking on the start button.

Fig. Startup menu

Icons:

Icons are the small graphical image used in GUI OS environment. It represents the symbolic meaning of the command, file, program, web page, etc. Icons help to execute commands, open programs or documents quickly. To execute a command by using an icon, click or double-click on the icon. An icon is a group of images of various formats (size and colors).

Fig. Icons

Window:

Windows are frames on the desktop that contains the contents of opened files, folders, and programs. In other words, it is usually a rectangular portion of the display on a computer monitor that presents its contents (e.g. the contents of a directory, a text file or an image) on the screen. Windows are one of the elements that comprise a graphical user interface (GUI).

Task Bar:

The taskbar displays opened files, folders, and programs. When multiple windows are open, you can click on the file, folder or program buttons in the taskbar to switch between windows.

Fig. Task Bar

List of components of tasks bar:

1. Start button
2. Quick launch bar
3. System trays with some programs
4. Time bar

For example, all documents using the same extension have the same icon. Some folders can have a customized icon applied to them. The name of file, folder or program is displayed under the icon.

Computer:

Computer folder displays all hard disk drives and removable storage devices connected to your computer. Double-clicking on a drive or removable storage device displays its contents.

Fig. Computer

To open the computer Folder:

1. Click on start Icon>Computer or double-click on the Computer icon.

Documents:

Documents folder provides a place to store all of your files. When you save a document, the default save location is the Documents folder:

Fig. Documents

To open the Documents Folder:

1. Click Start>Documents or Double-Click.
2. Networks
3. The Networks folder displays all the shared resources connected to your computer by a network.

Networks:

The Networks folder display all the shared resources connected to your computer by a network.

Fig. Networks

To open the Network Folders:

1. Click start>Networks or Double-click on the Networks.

Recycle Bin:

When you delete a program, file or folder, it is moved to the Recycle Bin. The Recycle Bin gives you the opportunity of retrieving your deleted items later if you change your minds. Items in the Recycle Bin still take up hard disk space.

Fig. Recycle bin

When the Recycle Bin is full, Windows automatically cleans out enough space to accommodate the newest deleted items. By default, the Recycle Bin is located on your desktop.

To restore items from the Recycle Bin:

1. Double-click on the Recycle Bin on the desktop. This opens the Recycle Bin windows.
2. Select the items you want to restore.
3. Click the Restore this item link in the Recycle Bin Tasks area.

Music:

By default, the Music folder is situated in the Libraries folder. When you use Windows Media Player to copy music from a CD or download music from the Internet, the default save location is the music folder.

Fig. Music

To open the Music folder:

1. Click start>Music.

Pictures:

By default, my pictures folder is situated in the libraries folder. When you save pictures from your digital camera or scanner to your computer or save a file in a graphics program, such as Microsoft Paint, the default save location is the pictures folder.

Fig. Pictures

To open the Pictures folder:

1. Click start>My pictures.

2. Working with files and folders

Folder:

Folders on a computer provide a storage system similar to folders in a filing cabinet. Folders can contain files and other subfolders. Windows provides a number of personal folders to start your computer filing system. A folder is typically represented by a folder icon. The folder name is the icon. The folder in Windows is also known as a directory in DOS.

Fig. Folders

Creating the personal folder on the desktop:

1. Right click on the desktop.
2. Select New>folder.
3. Give the name of the folder then press enter.

Alternative way to create the personal folder:

1. Click on the file>folder.
2. Give the name of the folder then press enter.

Operating a file or folder:

1. Double-click on the file or folder you want to open.
2. The file or folder is displayed in a window.

To copy or cut files and folders:

1. Right click on the file or folder you want to copy or cut.
2. From the pop-up menu, Select Copy or cut.
3. Open the location you want the copied or cut item to be placed.
4. Right-click in the location.
5. From the pop-up menu, select paste.

To rename files and folders:

1. Right-click on the file or folder you want to rename.
2. From the pop-up menu, select rename.
3. Type a new name.
4. Press the Enter key on your keyboard.

To delete a file or folder location in a folder:

1. Select the file or folder you want to delete.
2. Right, click on the file or folder you want to delete.
3. From the pop-up menu, select Delete.

OR

1. Select the file or folder you want to delete.
2. Press the Delete key on your keyboard.

Changing File and Folder Views:

Fig. Changing file and folder views

To change how the files and folders within a folder are viewed:

1. Click the Change your Views option.
2. Select the file and folder view you want.

Display File and Folder Properties:

Files and folders have property sheets that include information such as the type, size and location of file or folder; the data of a file or folder was created, modified or accessed; file and folder attributes; the name of the program that opens a file and the number of files or subfolders contained in a folder.

To display properties for files and folders within a folder window:

1. Select the file or folder (in the folder window) for which you want to display properties.
2. Right –click on the file or folder for which you want to display properties.
3. From the pop-up menu, select properties.

Modifying Folder Options:

1. Open the folder for which you want to modify.
2. Select Organize> Folder and Search Options.
3. This opens the folder Options dialog box.
4. Make the folder modifications you want
5. Click OK.

Using Task Panels:

Task panels provide an easy way to access the most commonly used folder tasks. The task panel displays a list of hyperlinked tasks to the left of the folder contents.

Fig. Using task panel

Several folders offer additional specialized hyperlinked tasks. For example, the pictures and Music folders offer links that help you manage your picture and music files. The recycle bin offers links to empty the Recycle Bin or restore items from Recycle Bin.

Computer folders offer links to view system information, add or remove programs, and change system settings.

Searching Files/ folders using search companion:

Fig. Searching files and folders

Enhanced for Windows 7, the Search Companion is designed to help you quickly find what you`re looking for.

1. Click start Icon
2. Type whatever you want to search.

3. Working with a Windows Application Program

Customizing the Desktop:

By default, the Windows theme is applied the first time you start Windows. A desktop theme affects the whole look of your desktop.

Fig. Customizing the desktop

To apply a desktop theme:

1. Right click a desktop.
2. From the pop-up menu, select personalize. This opens the Personalization dialog box.
3. Select a theme from the Theme option.

To apply a desktop background:

1. Right click on the Desktop.
2. From the pop-up menu, select Personalize. This opens the Personalization dialog box.
3. Click the Desktop Background option.
4. Select a background from Background list.
5. Click on Save Changes.

Control Panel:

As you`ve read earlier Control panel is one of the most important system folders, which consist of various controlling program`s icon to control an overall operation of the Windows. The following is the Sample of Control panel.

Fig. Control panel

Date and Time:

With the help of this option, we can change / set our system date and time as we need.

Display:

This option is to customize the Desktop environment.

Keyboard:

We can set keyboard settings like its character repetition and cursor blinking rate, a width of the cursor.

Program and Features:

This option allows the user to do following things;

Allows users to uninstall and change existing software packages, as well as indicating how much space individual programs take and how frequently they are used.

1. Allows users to manually install software and install add-ons from Windows Update.
2. Allows users to change which Windows components are installed.

Administrative Tools:

This option contains tools for system administration, including security, performance, and service configuration. These are the links to various configurations of the Microsoft Management Console such as the local services list and the Even Viewer.

Windows Update:

This option is used to specify how the automatic updates client should download updates from Microsoft update website, by default this is set to download and install daily.

Windows Keyboard Shortcuts:

Use shortcut keys as an alternative to the mouse when working Windows. You can open, close and navigate the Start menu, desktop, menus dialogue boxes and Web pages using keyboard shortcuts. It makes users use Windows easy.

3.4 OSOS (Open Source Operating System)

It is an operating system that is free to use and which provides the original code where the source code is available (under a copyright license) to the public, which enables them to use, modify/ enhance the operating system, and redistribute the modified (or unmodified) form of the operating system.

Some examples of OSOS are Linux, Free BSD,Open BSD, Open Solaries and Free DOS et

The characteristics of OS

• Free Redistribution of software and code.
• Derived works.
• Integrity of the author’s source code.
• No Discrimination against Persons, Groups or Field.
• Distribution of license.
• License must not restrict other software.

Advantage of OSS

• It is free or has to pay nominal fee.
• It does not require buying license published by company.
• Multiple distribution.
• It software are freely available on the internet with coding.

Disadvantage of OSS

• No support is available.
• It product may not be fully tested or modified by inexperienced developer, hence it can cause

problem on computer.

• OSS are not popular in market.
• Limited choice of application software.
• OSS are complex to use.

Introduction to UNIX and LINUX
UNIX:

UNIX is a popular open source operating system used in large variety of scientific, engineering and mission critical applications. UNIX was written in Assembly language at first and then re-written in C programming language and other machine independent languages by Dennis Ritchie and Ken Thompson at AT&T in 1968.

• UNIX is an OS designed for use on any kind of computer or computing device.
• Current versions of UNIX are running on everything from supercomputers to mobile phones.
• It has GUI based.
• UNIX is also an attractive tool for internetworking.
• The different versions of UNIX are Sun Solaris, GNU/Linux, and MacOS X.

Features of UNIX

• Multiuser OS
• Multitasking OS
• Reliable and Efficient OS
• Portability OS

Linux

Linux is a free open-source operating system based on UNIX. Linux was originally created by Linus Torvalds with the assistance of developers from around the globe. Linux is free to download, edit and distribute. Linux is very powerful operating system. Linux is widely used for both home and office uses. It is the main OS used for high performance business and in web servers.

Advantage of Linux

Low cost.

Stability

Performance

Networking

Flexibility

Compatibility

Wider Choice

Fast and easy installation

Better use of hard disk

Multitasking

Security

Some Basic Terms:

Spooling: The term spooling is derived from the term SPOOL (Simulation peripheral operation On-line). A spool is a buffer used in spooling. Spooling is a process used to balance the difference of high-speed of the CPU and slow speed of the input/output devices. It is primarily used for printing purpose. When we provide multiple files to print together to a printer, although the printer can print one file at a time. But, all files get lined up in a queue and get printed one-by-one. In this process, CPU remains free and the user can work on other applications. This technique of printing is possible through a capability of the operating system known as spooling.

Scheduling: When more than one process is able to run, the operating system must decide which one to run first. This part of the operating system concerned with this process, so it is called scheduler and it uses the algorithm which is called scheduling algorithm.

Unit Wise Important Questions for Computer Science XI

Unit 7 Application Package

1. What is word processing? Write its features.
2. What do you understand by formatting a document?
3. What is a word processor? State the advantages of the word processor.
4. Write short notes: a) Mail Merge             b) Hyperlink and bookmark
5. What is spreadsheet package? State the advantages of the spreadsheet packages.
6. What is an application program? List the major features of the spreadsheet.
7. Write short notes: a) Cell b) The Goal Seeks            c) Conditional formatting               d) what if analysis
8. What is a presentation package? Explain with its features.
9. What is Database management system? Write its characteristics.
10. Describes the types of domain specific tools.

Unit-4 Application Package

4.1 Introduction to Office Package

4.1.1 Word Processing

Word Processing is an application of computer technology for typing and manipulating any kind of text such as letters, memos, articles, brochures, proposals, thesis, reports, books, etc. A word processor is a software package that provides a working environment to type, manipulate, edit, format, save, retrieve and print any kind of text. Some of the commonly used word processor is Word perfect, word star, Ms-word, page maker, etc.

Features of word Processor

• Fast operation
• Editing text features.
• Formatting features.
• Permanent Storage
• OLE (Object linking and embedding)
• Review the document
• Mail Merge
• Searching
• Print Design

Some Popular Word Processing Packages.

MS word         MS write         AmiPro            Word Star       Kingsoft Writer            Lotus Notes

Lotus Word Pro           Professional Write                  MultiMate                  Word Perfect

Apache Open Office Writer    Ted

Mail Merge

Mail Merge is the processing of merging (combining) the mail (letter/invitation card etc) document with the name list of different recipients individually. In Microsoft, the mail merge features makes it easy to send same letter to a list of different people with correct name and address printed on each letter.

Use of a word processor

• To create resume/bio-data
• Cover letters
• Advertisements
• Reports writings
• Update a blog
• World Wide Web Pages
• Newsletters
• Annual Reports
• Articles
• Directories
• Brochures
• Books

MS Word

We know that Microsoft Word (Ms-Word) is the most popular word processing software package developed by Microsoft Corporation. It runs in the windows platform. It provides several functions beside entering, creating, editing, formatting, saving, retrieving and printing document. The files created in Microsoft word is called word document. File extension is .doc.

 Microsoft Company is releasing different versions of Ms-Word such as, Ms-Word 97, Ms-Word 2000, Ms-Word 2002, Ms-Word 2003, Ms-Word 2007, Ms- Word 2010, Ms- Word 2013, Ms- Word 2016 and Ms- Word 2019. It does not really matter which version of Ms-Word we are using. The icons and menus might look different but the functions are almost the same.

Macro:

A macro is a list of commands, keystrokes or some other actions that has been saved and given a name when you create a macro; we record a series of actions. When we replay the macro, it repeats those actions for us. We can use macro to automate nearly any task that requires multiple steps-no matter how many steps are required.

Many commercial applications supports macros and some even feature an array of built-in, predefined macros that we can use right away to suit our own work style.

Document Formatting:

It includes size of page, its orientation, headers or footers, merging columns & sections, Due to this, document look like good.

Templates:

            Templates are redesigned documents that are blank except for present margins, fonts, paragraph formats; use a template we do not have to manually format complex documents. We can open a document template, type our text into it, save it and print the finished document.

4.1.2 Spreadsheet Package

Introduction:

Microsoft Excel (Ms-Excel) is one of the most popular types of spreadsheet package. This is developed by Microsoft Corporation, U.S.A. You can Ms- Excel to prepare salary sheet, Balance Sheet of company, profit and loss account etc. It can be used to solve arithmetical, algebraic, trigonometric and statistical problems. The file of Ms-Excel is called workbook and its extension is .XLS. An exe file of Ms-Excel is ‘Excel. Each excel worksheet consists of 256 columns and 65,536 rows.

Features of Spreadsheet

• Allows data entry, storage, calculations and presentation.
• Formatting of data for making it attractive by using tools like font, font color, font size.
• Simple computing operations like copy, cut, paste, find, replace.
• Sorting data either or ascending or descending order on the basis of different fields.
• The formula for calculations using cell address including mathematical, statistical, trigonometrically etc.
• Allow sharing workbooks, allowing multiple users to edit the same workbook at the same time.
• Provide various chart types and shapes like pie, Bar, XY, Stack Bar, Area, 3D-Pie.
• Data validation for setting data entry rules.
• Internet features including a web toolbar and the ability to create hyperlinks and to save files using Save as HTML option.
• Advanced Features like goal seek, scenario, auditing, what if analysis pivot table pivot chart.
• Supports the high level features of object linking and embedding i.e. data from MS Word can be safely and easily put and linked with data in MS Excel and vice versa.
• Support natural language formulas.

Spreadsheet Software’s

MS Excel         Gnumeric        Lotus1-2-3       Simple Spreadsheet   Google Spreadsheet                           OpenOffice.org Calc               WikiCalc          Ability Office Spreadsheet   TABULUS

Use of Spreadsheet

• Arithmetic and Statistical Calculations
• Preparation of Profit and Loss Account.
• Financial Forecasting
• Reports and Balance Sheet.
• Preparation of Income Statements.
• Charts (PIE, BAR etc)
• Regression Analysis
• Preparation of Tax Statements
• Database Management Developing Custom Application Using Visual Basic Application.

Basic Fundamental of Spread Sheet

Workbook: –

Workbook is a collection of one or more worksheets. A workbook is a file in which you work because each workbook can contain many sheets. You can organize various kinds of related information in a single file.

Worksheet: –

It is an area of workplace where the data or record can be placed. In each and every worksheet there are 256 columns and 65,536 rows, columns and rows are presented by A,B,C …..IV and 1,2,3…… 65,536 respectively.

• Rows: – The horizontal line of worksheet.
• Columns: – The vertical line of worksheet.

NOTE: – We can put 255 sheets in workbook of excel.

Cell: –

The intersection between row and column is called cell. It is unit part of worksheet, which can store information, as pictures text, number and formula. Each cell contains 32,000 characters.

Cell Range: –

It is an area or collection of defined number of cells into a worksheet that refers to a certain block of cell. Example: A1:E1, A1:C4 etc.

Cell Address (Cell Reference): –

It is the reference of a cell denoted by using the column label followed by row number. In spreadsheet terminology, a cells column and rows co-ordinate is called the cell reference. Example: A1, B2, C4, E9 etc.

4.1.3 Presentation (Power point)

Introduction:

Power point is a presentation package. When we have many pictures, texts, graphics, information’s, sounds, video-clip to present this to a large number of people we use this package.

Features:

• Presentation gives detail overview of the topic.
• Audio-Video can be merged on the single to clarify on specific topic.
• It is easy to build from simple to interactive presentation.
• It provides wide range of design, animation and other built in tools for easiness.
• Presentation software provides 2D and 3D text editing and displaying facilities.
• Presentation software can be converted to movie file, so that it can be used as title and names displayer from the beginning or at last of the movie.

Use of Presentation Program

• An editor that allows text to be inserted and formatted.
• A method for inserting and manipulating graphic images and
• A slide show system to display the content.
• The Presentation Program is application software used for creating a slide, designing it, formatting it, setting animation and sound, setting effects and displaying the slides.

Examples of Presentation Program are

            MS PowerPoint        Simple Slides             IBM Lotus      KPresenter            OpenOffice.org Impress

            Opera Show Format            Magic Point   Corel Presentations             Freelance Graphics

            Apple Keynote                      Power dot                  Harvard Graphics

Features of Presentation Package

• Allows data entry, storage, Calculations and presentation
• Formatting of data for making it attractive by using tools like font, font color , font size etc.
• Simple Computing operations like copy, cut, paste, find, replace.
• Pre-designed slide designs can use used faster and easier development of the presentation.
• Slide Transition, to define how a slide is displayed from the previous one.
• Predefined Slide animation for making the slide look attractive.
• Custom animation to develop our own animation.
• Buttons for the easier navigation from one slide to another.
• Bookmark and Hyperlink to link different components of a presentation.
• Provide various chart types and shapes like pie, Bar, XY, Stack Bar, Area, 3D-Pie.
• Internet features including a Web toolbar and the ability to create hyperlink and to save files using Save as HTML option.

Database Management System

Database:

It is organized form of record about some person, organization or something store under certain media. It is a collection of related information about a subject organized in a useful manner that provides a base or foundation for procedure, such as retrieving information, drawing conclusion and make decision.

DBMS:

Database Management System is software that manages the data stored in a database. This is a collection of software which is used to store data, records, process them and obtain desired information. Since, data are very important to the end users, we must have a good way of managing data.

A DBMS is a collection of programs that manages the database structure and controls access to the data stored in the database. The DBMS make it possible to share the data in the database among multiple applications or users. The DBMS stands between the database and the user.

Some major database System activities are (Functions of DBMS)

1. Adding new file to the database
2. Inserting data into the database
3. Retrieving/viewing data from the database
4. Updating data in existing database file
5. Deleting data from the database file
6. Removing files from the database

Advantages of DBMS (Features /Objectives of DBMS)

1. Sharing data
2. Reduced data redundancy
3. Data backup and recovery
4. Inconsistency avoided
5. Data integrity
6. Data security
7. Data independence
8. Multiple user interfaces
9. Process complex query

Concept of MS Access

Features of Microsoft Access:

• It provides very useful database features such as tables, forms, reports and queries.
• It works as front end development tool.
• This provides end-user applications developer environment.
• It shares data with other application such as Microsoft Word or Excel.
• It support three computer programming language such as: SQL, Macros and Visual BASIC etc.

4.2 Introduction to Domain- Specific Tools

Domains-specific tools refer to the application software developed and used for some specific domain (or area). It is developed to fulfill the requirement of a specific domain. Some of the common domain specific tools are:

• School Management System
• Inventory Management System
• Payroll System
• Financial Accounting System
• Hotel Management System
• Weather Forecasting System

Unit Wise Important Questions for Computer Science XI

Unit 5 Programming Concepts and Logics 

• What is program?
• What is programming language? Explain its types with merits and demerits.
• Differentiate between compiler and interpreter.
• What is error? Briefly explain its types.
• Differentiate between syntax and semantics error.
• Define algorithm and flowchart with examples.
• What is C? Write its Features.
• What is a Data type? Explain the type of operator with examples.
• What is control structure? Write different between break and continue statement with examples.
• What is looping? Write different between while and Do while loop with examples.
• Define the term array. What is string? Explain any four string handling function with example.

Unit 5- Programming Concepts and Logics

5.1 Programming Concept

PROGRAMMING CONCEPTS

Program:

Program is a group of instructions given to the computer to perform a certain task. A program is used to solve a problem in computers. The program is written using a series of instruction that consists of all symbols, characters and certain rules.

A computer specialist who is responsible for designing, writing and modifying computer program is known as computer programmer. Programmer had depth knowledge about programming tools, techniques and programming language.

Feature of good program

• Integrity: A program should be complete and must give the desire output.
• Clarity: A program should be clear and should not be ambiguously.
• Simplicity: A method for solving a problem should be very simple and easily understandable.
• Efficiency: A program should take less memory and processing time, as a result it runs faster. Such kind of program automatically increases the efficiency of computer.
• Maintainability: A program should be easy to maintain and update in future.
• Reliability: It should be reliable so that user can depend on it.
• Generality: It should be flexible and easy to operate with a wide range of platform.
• Modularity: A program should be divided into different modules in order to complete a complex problem.
• Robustness: A program should be almost 100 % perfect.
• Documented: Documentation helps for smooth operation for the users and even helps for further modification and maintenance.

Computer Program:

Computer program is a group of instructions given to the computer to perform a certain task. A program is used to solve a problem in computers. The program is written using a series of instruction that consists of all symbols, characters and certain rules.

 Programming Language:

The process of writing computer using such rules and symbols is called computer programming or coding. Computer programming is used to prepare computer programs and software.

The language which is used to develop program in computer is called programming language. Being an electronic machine, computer can understand only binary code i.e. 0 and 1 represented by the flow of electricity in the form of ‘ON’ and ‘OFF’ in voltage.

Every programming language consists of a set of codes that a computer programmer uses to give instruction to computer to perform some specific task. The set of rules to write the code is called syntax. The computer understand the code after it is complied.

Nowadays there are many programming language for making program in computer. For example: C, C++, VB, .NET, Java etc.

Differences between Program and Software

Type

s of computer programming Language

• Low Level Language

1. Machine Level Language ( First Generation Language)
2. Assembly Level Language
   • High Level Language
     1. Procedural language
     2. Problem oriented language

• Natural Language

Low Level Language:

            Low level language is a machine oriented or depended language in which detail knowledge of hardware specification is required to run the program. Statements in Low Level language are written based on the hardware structure of the computer. The low level language is divided into two types:

Machine Level Language:

            The machine language which is written in the form of binary 0’s and 1’s. The machine level language is directly understand by computer because it is written in the form of 0’s and 1’s. Each instruction of the machine level language tells computer what to perform. The programs written in machine level language are executed very fast than the program written in any other language.

            Object Program                                              Processor

            Program in machine Level Language 

Advantage

• Program execution is faster than other language.
• It does not require any translating program.

Disadvantages

• Machine Level Language are machine dependent
• It is difficult to perform the machine level language.
• Program development is time consuming.
• There is a greater chance of error in the programming.
• Need to higher level of skill programmer.

Assembly Level Language:

                           Assembly Level Language is a low level machine dependent language in which the symbolic codes (Mnemonic codes) are used to write assembly programs. With the use of symbolic codes in assembly language, it is easy to write the program for the programmer. For example ADD for addition, SUB for Subtraction, CMP for Comparison. It is easier to understand, find error and correct error. The program written in assembly language needs to be translated into the machine level language. This is done by an assembler an assembler translates the assembly level language into the machine language.

      Source program                     Assembler              Object Program             Processor                                   

              Program in ALL                                   Translator                   Program in MLL

Advantage

• It is easy to understand
• It is easy to find and correct error.
• It is easier to modify.
• Program Execution is faster than High level language

Disadvantage

• It is machine dependent language.
• Program development and debugging is more difficult and time consuming than HLL.
• It is very hard to remember the mnemonics
• It required translating program.

High Level Language:

                           High Level languages are the language which uses human language and mathematical notations. High level language uses the English keywords and mathematical symbols to write the program rather than mnemonics codes used in assembly language. High level languages are machine independent. While using high level language the program is not concerned about the machine structure of the computer. The high level language is to be translated into machine level language. This task is done by using the compilers and interpreters. These are also called translating program. The program written using high level language is easier to maintain than low level language. Advanced program can be developed using high level programming language. Some of the common high level language is: BASIC, PASCAL, FORTRAN, C, C++, Java etc.

      Source program                    Compiler/Interpreter                Object Program             Processor               Program in HLL                 Translator                   Program in MLL

Advantage

• It is machine independent
• It is easier to learn and develop
• Easily detect and remove errors.
• It is easier to maintain.
• Lower programming cost.
• Better documentation.
• Programmer does not need to remember large no. of mnemonics.
• No need to knowledge of internal structure of computer architecture for writing source program in HLL.

Disadvantage

• Computer does not understand directly
• More time to require for execution of the program.
• Require more memory space
• Less flexibility
• It needs to be translating program.
• Operating speed is slow.

High Level Language can be further categories as:

1. Procedural oriented language (3GL)
2. Problem oriented language (4GL)

• Natural Language (5GL)

Differentiate between Assembly level language and Machine level language.

Fourth Generation Language:

                           Fourth generation language was developed after HLL, so it is one step ahead from HLL. It is result/problem oriented programming language and it contains database query language. Fourth generation language program is also needed to be translated either by compiler or interpreter into machine understandable code before they are executed as it is not directly understood by the computer. Example of 4GL is SQL (Structure Query Language), Visual Basic, C#, PHP.

Language Processor (Translator)

                           Language Processor is the programs that translate the program written in other language (source program) to the machine level language program (object program). They are three types.

1. Assembler:

                           An assembler is a translator or translating program which translates codes of assembly language into equivalent machine level code. The program which is to be translated by assembler is called source program and the translated program by assembler is object program.

      Source program                         Assembler                               Object Program             Processor                   

       Program in ALL                             Translator                   Program in MLL

1. Compiler:

                           A compiler is a translating program that translates the program written in high level language into equivalent machine level language at once. The program written in high level language is called source program and the program translated into machine language is called object program.

      Source program                         Compiler                    Object Program             Processor                   

       Program in HLL/4GL             Translator                                 Program in MLL

1. Interpreter:

                           An interpreter is a translating program which translates the program written using high level language into equivalent machine level language one line at a time. It is similar to compiler but it converts the program’s one line at a time into machine level language.

      Source program                         Interpreter                              Object Program             Processor                   

       Program in HLL/4GL             Translator                                 Program in MLL

Differentiate between Compiler and Interpreter.

List of high level programming language

• FORTRAN: Formula Translator is the first High Level Language which is very powerful language for scientific and engineering computations.
• LISP: List Processing language is functional language for list processing, recursive, and not iterative. It is suitable for solving non numeric operations and used in the field of AI (Artificial Intelligence) and pattern recognition.
• CPL: Combined Programming Language is used polymorphic testing structures and it has list and array. It was a step toward the design of the c language.
• COBOL: Common Business Oriented Language is a classical procedural language aimed at enterprise management.
• BASIC: Beginner’s All- purpose Symbolic Instruction Code.
• BCPL: Basic Combined Programming Language is also uses procedures and functions.
• PASCAL: PASCAL is a structured programming language.
• PROLOG: Programming Logic language is used for solving natural logic and in the field of knowledge based system which is a branch of AI.
• C: C is a procedural programming language.
• C++: It is also called Object Oriented version of C, powerful and efficient language for developing software.
• JAVA: Java is also Object Oriented Programming Language for internet web and mobile applications.
• .NET: It is read as ‘dot NET’ is powerful features of different programming language into one environment. It is most commonly used for solving web based applications and distributed mobile applications.
• XML: eXtensible Markup Language is more advanced markup language than HTML for web content development. It helps to manages sources document in several different formats such as web page, printable documents, PDF files etc.
• JavaScript: JavaScript is a scripting language. It can run inside simple web browser application and calculation. It shares the syntax of C or Java.
• ASP: Active Server Page is server site web scripting language developed by Microsoft Corporation for accessing database from web application.
• PERL: Practical Extraction and Reporting Language is one of the first scripting languages on UNIX system. It is open source and found on UNIX/Linux based server.
• PHP: Hypertext Preprocessor is very popular server site scripting language on UNIX/Linux system. It is very popular for accessing database like My SQL and Oracle. It is open source software.

Testing and Debugging

Bug / Error: Errors are the mistake in the program. The Error can be in syntax or logic of the program.

Testing: Testing is the process of making sure that the program performs the intended task.

There are several stages of testing. They are:

• Unit testing involves the individual components’ testing.

• Integration testing involves the separate components’ testing as they are put together.

• System testing that involves the whole final form of a program testing.

• User acceptance testing involves the user testing the program to see that it is the result what is required.

Debugging: Debugging is the processing of discovery and correction of programming errors (bugs).

• Many syntax and logical errors might have occurred while writing a program.
• Debugging a program can take from a few seconds to months and even years depending on the bug, size of a program and type of system programmer etc.

Syntax and Semantics (Logical) errors

Syntax / Logical: Syntax is the arrangement of words into a sentence. It describes the rules by which words can be combined to make a meaningful sentence. For eg. S.+V.+O. The syntax defines whether the instruction is correct or not. If the syntax of the program is not correct, then the compiler or interpreter detects an error called syntax error and informs the programmer. Then the program execution gets terminated.

Semantic: Semantic is the study of meaning in language. It defines what the sentence means. Although the syntax is correct, it may not be meaningful. For eg.

                                    Aryan eats an apple.   = Syntactically and semantically correct.

                                    Aryan eats a house.    = Syntactically correct and but semantically not correct.

                                    Aryan eat a house.     = Syntactically and semantically incorrect.

Runtime Error: The error which appears during the execution or runtime of program is called runtime error. The error which appears during the execution or runtime of a program is called runtime error. Such errors appear when the computer is asked to divide by zero or when the variable is assigned a large value which is beyond its capacity. The run-time error causes the termination of program execution.

Programming Fundamentals

Data types

Introduction to Data Type:-

• Data type specifies the type of data that is to be used in a program.
• A data types defines the set of data in any high level language which specifies the values and stored in memory.
  1. Integer: All positive natural numbers, negative natural numbers and zero are called integers. Integer variable can take two bytes memory hold data in computer.
  2. Characters and String: All alphabets including uppercase, lowercase, symbols etc are considered as character. Even space is also considered as a character. It requires one byte memory to hold the data in computer.
  3. Numeric Real: The data type which contains any numeric representation is called real data type. The value may be signed or unsigned, fractions or exponential as well. Example: 0, 0.5, 4.7234, 3.0e^-4, etc are real numbers.
     
     
  4. Floating:- All fractional numbers are considered as floating point numbers. Variables like: weight, height, currency etc. It requires four bytes memory to hold the data in computer.
  5. Boolean: A Boolean data type can only take two data values: either true(1) or false(0). For eg. Marital status of a person is either married or unmarried.

Keyword, Variable and Constant

Keyword:

Keyword is a special reserved word in programming language whose meaning has been already defined to the compiler. A keyword performs a specific task in computer program. For eg.int, float, if, while, etc.

Variable:

Variable is a named location in memory (RAM) of computer which can hold some value. The value assigned to the variable may be changed during the execution of the program, hence it is called variable. For eg. L=10 and B=5, here L and B are variable and 10 and 5 are value.

Constant:

It is a value which does not change during the execution of the program. For eg. A=10 and B=5 are constants.

Operation, Operand and Operator

Operation:      An Operation in program is defined as an action upon the given data. The examples of operation are as follows:

• Arithmetic Operation
• Relational Operation
• I/O Operation
• Data Moving Operation etc.

Operand:        Operand is the different type of data on which different operations take place. The data may be value or variable.

Operator:       An Operator is a sign or symbol which performs an operation or evaluation on one or more operands. There are different types of operator they are Arithmetic Operator (+,-,*,/,%), Relational Operator (=,>,<,>=,<=,!=), Logical Operator (AND, OR and NOT) etc. 

Program Design Tools

Algorithms:

An algorithm is a step by step by of instructions to solve a particular problem. It is an effective procedure for solving a problem in a finite number of steps. It is written in simple English language.

• It should be finite number of steps.
• It should be in a simple language.
• It should have an input.
• It should give an output after its execution.
• It should be independent of programming language.

Example: Write an algorithm to read the principle amount, time and rate and find simple interest.

1. Start / Begin
2. Read / Input P,T and R.
3. Calculate SI=P*T*R/100.
4. Print / Display SI.
5. End / Close.

Flowchart:

A flowchart is a graphical representation of program logic in terms of symbols. It represents the program using the symbols. It is a program planning tool for organizing the sequence of steps necessary to solve a problem.

Types of Flowchart

1. System flowchart: The flowchart which shows the overview of the data flow and sequence of operations in a system is called system flowchart.
2. Program Flowchart: The flowchart which shows the detailed diagram to solve a particular problem of the program is called program flowchart.