Tuesday, June 28, 2011

Class IX, COMPUTER, "Introduction to Computers"


A Computer is an automatic electronic, calculating device which can process a given input in a prescribed manner to produce a desired output, at a very high speed with remarkable accuracy. It can also perform all arithmetic and logical functions according to instructions given in a systematic order to solve any problem and produce processed information.

Advantages of Computers


Since Computer is an electronic machine and electrical pulses travel at the rate of passage of electric current. This speed enables the computer to perform millions of calculations per second.


A computer has too much storage capacity. Once recorded, a piece of information can never be forgotten.

High Accuracy

A computer can be considered as 100% accurate. Checking circuits are built directly into the computer, that computer errors that undetected are extremely rare.


Computer can perform any task, provided it can be reduced to a series of logical steps.


Computer never gets tired. It performs most boring, repetitive and monotnous task.

Automatic Operation

Once a program is fed into computer the individual instructions are processed on after the other. Thus computer works automatically without manual intervention.


The ability to take in and store a sequence of instructions for the computer to obey. Such a sequence of instruction is called a PROGRAM and it must be written in the Computer Language.

Decision Making Capability

Computer can take simple decisions, such as less than, greater than or equal to. It also determines whether a statement is true or false.


The physical components and other attached input and output devices of computers are called Hardware. All Hardware components may be connected mechanically, electrically or electronically with each other. Hardware includes input/output devices, CPU, backing storage devices and electronic circuit.


Computer required a number of instructions to do any job. The set of these instructions forms programs. Numbers of programs are combined for some purposes are called software.
They are designed by manufactures and programmers.

Types of Software

1. System Software
2. Application Software

Ages of Computer

At the early age people used pebbles, stones, sticks, scratches, symbols and finger tips to count, which were later replaced by numbers.
The history of computing is divided into three ages during which man invented and improved different types of calculating machines. These ages are,
Dark age – 300 BC to 1890
Middle age – 1890 AD to 1944
Modern age – since 1944 AD

Dark Age (3000 BC to 1890 AD


About 3000 years BC, Chinese developed the first calculating machine named Abacus or Soroban.
Abacus consists of a rectangular wooden frame having rods which carry round beads. Counting is done by shifting the beads from one side to another.


In 1632 AD William Oughtred, an English mathematician developed a slide rule. This device consists of two movable rules placed side by side on which number were marked.


Blasé Pascal (1623-1662), a French developed the first mechanical calculating machine in 1642. This machine consists of gears, wheels and dials. It was capable of adding and subtracting operations.


In 1671, a German, Gottfried Von Leibnitz (1646-1716) improved Pascal’s calculator to make it capable of performing all maths operations.


In 1801, a French, Joseph Marie Jacquard developed the first punch card machine.


Charles Babbage (1792-1871) an English mathematician also called Father of modern computer. As he gave the true concept of computer at Cambridge University, he developed Babbage Difference Engine in 1823 and Babbage Analytical Engine in 1833.
Lady Ada Augusta an assistant of Babbage is called the first programmer.

Middle Age (1890 AD TO 1944 AD)


In 1880s Herman Hollerith an American developed a machine which used punch card system. The machine could sense and punch holes, recognize the number and make required calculations. This machine was first used in 1890s by American Census Bureau.


In 1937, Professor Howard Aiken build the first electro-mechanical computer Mark-1, by trying to combine Babbage’s theory and Hollerith’s punching technologies. He completed his project in 1944 with the help of IBM Engineers.
Mark 1 could multiply two, twenty digit numbers in 5 seconds and made a lot of noise. It had a shape like a monster about 50 feet long, 8 feet high, having wiring of length equal to distance from Lahore to Gilgit or Karachi to Bahawalpur (800km) and had thousand ends of electro-magnetic relays.


ABC a special purpose computer was developed in 1938 by Dr. John Vincent Atanasoff and Clifford Berry at Iowa State College, USA.

Modern Ages (Since 1944 AD)


In 1945, Dr. John Von Neuman suggested the concept of Automatic Data Processing (ADP) according to the stored program and data. ENIAC


Electronic Numerical Integrator And Calculator (ENIAC) was the first electronic computer made in 1946 by John Presper Eckert and John Williams Mauchly, at the University of Pennsylvania, USA. This was based on decimal number system and it has no memory.

It could perform 5000 additions or 350 multiplications in one second. It contained 18000 vacuum tubes, 70,000 resistors, 10,000 capacitors and 60,000 switches and occupied a two room car garage. It consumed 150 kW of power. It weighed 27 tons.


Electronic Delay Storage Automatic Computer (EDSAC) was first computer based on stored program concept. It was completed by Mourice Wilkes at Cambridge University in 1949.


Electronic Discrete Variable Automatic Computer (EDVAC) was built by John Williams Mauchly, John Presper Eckert at Moore School, Pennsylvania in 1951.


UNIVersal Automatic Computer (UNIVAC) was the first commercially used computer made by John Presper Eckert and John Williams Mauchly in June 14, 1951.

Classification of Computers According to Purpose

1. General Purpose Computers

General purpose computers are designed to solve a large variety of problems. The different programs can be used to solve many problems. Most digital computers are general purpose computers and used in business and commercial data processing.

2. Special Purpose Computers

A computer designed for machine control or process control would be different than a general purpose computer. The special purpose computers are designed to solve specific problems. The computer program for solving a specific problem is built right into the computer. Most analog computers are special purpose computers. These special purpose computers are widely used in industrial robotics.

Types of Computers

1. Analog Computers

Analog computers are used to process continuous data. Analog computers represent variables by physical quantities. Thus any computer which solve problem by translating physical conditions such as flow, temperature, pressure, angular position or voltage into related mechanical or electrical related circuits as an analog for the physical phenomenon being investigated in general it is a computer which uses an analog quantity and produces analog values as output. Thus an analog computer measures continuously. Analog computers are very much speedy. They produce their results very fast. But their results are approximately correct. All the analog computers are special purpose computers.

2. Digital Computers

Digital computer represents physical quantities with the help of digits or numbers. These numbers are used to perform Arithmetic calculations and also make logical decision to reach a conclusion, depending on, the data they receive from the user.

3. Hybrid Computers

Various specifically designed computers are with both digital and analog characteristics combining the advantages of analog and digital computers when working as a system. Hybrid computers are being used extensively in process control system where it is necessary to have a close representation with the physical world.
The hybrid system provides the good precision that can be attained with analog computers and the greater control that is possible with digital computers, plus the ability to accept the input data in either form.

Classification of Computers According to Size

1. Super Computers

Large scientific and research laboratories as well as the government organizations have extra ordinary demand for processing data which required tremendous processing speed, memory and other services which may not be provided with any other category to meet their needs. Therefore very large computers used are called Super Computers. These computers are extremely expensive and the speed is measured in billions of instructions per seconds.

2. Main Frame Computers

The most expensive, largest and the most quickest or speedy computer are called mainframe computers. These computers are used in large companies, factories, organizations etc. the mainframe computers are the most expensive computers, they cost more than 20 million rupees. In this computers 150 users are able to work on one C.P.U. The mainframes are able to process 1 to 8 bits at a time. They have several hundreds of megabytes of primary storage and operate at a speed measured in nano second.

3. Mini Computers

Mini computers are smaller than mainframes, both in size and other facilities such as speed, storage capacity and other services. They are versatile that they can be fitted where ever they are needed. Their speeds are rated between one and fifty million instructions per second (MIPS). They have primary storage in hundred to three hundred megabytes range with direct access storage device.

4. Micro Computers

These are the smallest range of computers. They were introduced in the early 70’s having less storing space and processing speed. Micro computers of todays are equivalent to the mini computers of yesterday in terms of performing and processing. They are also called “computer of a chip” because its entire circuitry is contained in one tiny chip. The micro computers have a wide range of applications including uses as portable computer that can be plugged into any wall.

5. Laptop Computers

The smallest computer in size has been developed. This type of small computers look like an office brief case and called “LAPTOP” computer. The laptops are also termed as “PORTABLE COMPUTERS.” Due to the small size and light weight, they become popular among the computer users. The businessmen found laptop very useful, during traveling and when they are far away frm their desktop computers. A typical laptop computer has all the facilities available in microcomputer. The smallest laptops are called “PALMTOP”.

Generations of Computer

First Generation of Computer (1946-1959)

Main Features

Major Innovation – Vacuum Tubes
Main Memory – Punched Cards
Input Output Devices – Punched cards and papers
Languages – Low level machine language
Operating System – No operating system, human operators to set
Size – Main frame for example ENIAC, EDVAC, UNIVAC
The duration lasted from 1946-1959 was based on vacuum tubes. These vacuum tubes were about the size of 100 watt light bulb and used as the internal computer component. However because thousands of such bulbs were used, the computers were very large and generate a large amount of heat, causing many problems in temperature regulation and climate control.
In this generation input and out put device (punched card) that was used fro data storing purpose were very slow. The computers were operating manually and the language used was a low level machine language (symbolic language) with binary code that required a high programming skill. ENIAC, EDVAC, UNIVAC and Mark-1 were some of the major inventions of this generation.

Advantages of First Generation

1. Vacuum tubes were used as electronic component.
2. Electronic digital computers were developed for the first time.
3. These computers were the fastest calculating devices of their time.
4. Computations were performed in millisecond.

Disadvantages of First Generation

1. Too large in size.
2. They were unreliable.
3. Induce a large amount of heat due to the vacuum tubes.
5. Not portable.
6. Limited commercial use.

Second Generation of Computers (1959-1964)

Main Features

Major Innovation – Transistors as main component.
Main Memory – RAM and ROM.
External Storage – Magnetic tapes and Magnetic Disk.
Input Output Devices – Magnetic tapes and Magnetic Disk.
Languages – Assembly language, some high level languages for Example BASIC, COBOL, FORTRAN.
Operating System – Human handles punched card.
Size – Main frame for example IBM-1401, NCR-300, IBM-600 etc.
The period of this generation is from 1959 to 1964. During this period transistor were used for internal logic circuits of computers. These computers could execute 200000 instructions per second. The input/output devices became much faster by the use of magnetic table. During this period the low level programing language were used however the high level programming languages such as FORTRAN and COBOL were also used. The problem of heat maintenance was solved and size of computer reduced, while speed and reliability were increased. Many companies manufactured second generation computers and many of those for business applications. The most popular second generation computer was IBM-1401, introduced in 1960, while the following computers were used by many business organizations. IBM-1400 series, IBM-1600 series, UNIVAC-III, NCR-300 etc.

Advantages of Second Generation

1. Smaller in size as compares to 1st generation.
2. Much more reliable.
3. Less heat generated.
4. Computation was performing in micro second.
5. Less hardware and maintenance problem.
6. Could be used for commercial use.

Disadvantages of Second Generation

1. Very costly for commercial use.
2. It still required frequent maintenance.
3. Frequent cooling also required.

Third Generation of Computers (1965-1970)

Main Features

Major Innovation – Integrated circuit (ICs) as basic electronic component.
Main Memory – PROM and DRAM.
External Storage – Improve disk (Floppy Disk)
Input and Output Devices – Keyboard for input, monitor for output.
Languages – More high level languages.
Operating System – Complete operating systems were introduced.
Size – Mini, for example: IBM SYSTEM / 360, ICH-360, HONEY WELL-316 etc.
In this generation the integrated circuits (IC) were used. Integrated circuits contain many electronic components on a single chip. The disk oriented systems wee made at the end of this generation. The size of computer became very small with better performance and reliability. High level programming languages were extensively used. In 1969 the first microprocessor chip INTEL 4004 was developed but it was used only in calculators. The faster input/output devices made possible multi-processing and multi programming. Where by a number of input terminals could be run virtually at the same time on a single centrally located computer. The famous computer were IBM-360, IBM-370, UNIVAC 9000 series etc.

Advantages of Third Generation

1. Smaller in size as compared to second generation.
2. More reliable.
3. Portable
4. Less electricity consumption.
5. Heat generation was rare.
6. General purpose computer.

Disadvantages of Third Generation

1. Air conditioning was required in many cases due to ICs.
2. Very advance technology was required to make the ICs.

Fourth Generation of Computers (1971-1981)

Main Features

Major Innovation – LSIC and VLSIC (Micro Processor)
Main Memory – EPROM and SRAM.
External Storage – Floppy Disk and Hard Disk.
Input and Output Devices – Monitor for output.
Languages – Languages and application softwares.
Operating System – MS-DOS and PC-DOS
Size – Micro computer e.g. IBM-PC, Apple Macintosh etc.
The Integrated circuits were more developed and called Small scale integration (SSI), after some time the SSI were more developed and termed as Large scale integration (LSI). There was a great versatility of input/output devices. In 1971, a powerful microprocessor chip INTEL 8008 was introduced. The first microprocessor which is used in personal computers (PC) was INTEL 8080. The 8 inch floppy disk was also introduced in 1971, while hard disk was introduced in 1973. The 5.25 floppy disk was first time used in 1978. The optical disk was developed in 1980. First portable computer “Osborne I” was marketed in 1981. IBM-3033, IBM-370, IBM system 34, IBM system 36, Cray-I, CP/M etc were introduced in this generation.

Advantages of Fourth Generation

1. Smaller in size and much reliable.
2. No cooling system required in many cases.
3. Much faster computation.
4. Portable and cheap.
5. The heat generated was negligible.
6. Totally general purpose computer.

Disadvantages of Fourth Generation

1. Very advanced technology was required to fabricate to the ICs.

Fifth Generation (1981-Onward)

Main Features

Major Innovations – ULSIC (Ultra large scale integrated circuit)
Main Memory – EEPROM, SIMM and DIMM.
External Storage – Modified magnetic and Optical disks.
Input/output Devices – Keyboard, Pointing Device, Scanner as input and Monitor as main output.
Languages – AI (Artificial Intelligence) Expert systems.
Operating System – GUI based e.g. Windows 95, Windows NT.
Size – Very small in size example: Laptop, Note book, Digital Diary, Palm top and Pocket PC.
This generation is started from 1981 and still continued, new technologies are adopted to fabricate IC chips, such as electron beam, X-rays or laser rays. The Very Large Scale Integration
(VLSI) was developed, so the computer became much smaller than ever before. New memory storage device like bubble memory, optical or memory are being designed. the new computer will be controlled by using human voice and will work by giving command in our own language. Future computer will in some way to be intelligent and capable of making decision.

Advantages of Fifth Generation

1. Very large storage capacity.
2. Long bit processor builds.
3. Artificial Intelligence Language developed.

Short Notes

1. Super Computer

These are the largest and fastest machines today where numerical computations are carried out speeds of up to 50 millions operation per second. Super computers are very sophisticated machines designed to perform complex calculations at fastest speeds. Super computers are used to model very large dynamic systems, such as weather patterns national or global weather forecasting, satellite tracking, cold-testing of atomic and nuclear weapon etc. Carry research and Intel are well known producers of Super Computers.

2. Main Frames

A main frame originally meant the cabinet containing the central processor unit of a very large computer. After mini computer became available, the word main-frame comes to refers to the large computer itself.
Mainframes, the biggest and the most productive general purpose systems, that are made to model large dynamic computing need of a big organizations that serve hundreds of terminals all at the same time. A terminal consists of a monitor and keyboard that allow a person to enter information and retrieve it from the computer. These computers are the ultimate in sophistication, flexibility and speed.

3. Mini-Computer

Mini computer are increasingly powerful and do almost any thing that large computers do, only more slowly and at much lower cost than mainframes. This makes it ideal for small companies where capacity and speed of operations in not highly critical. These computers are smaller than mainframe and larger than micro computer in size. A mini computer is a multiprocessing system having terminals attached to it and is capable of supporting 4 to 200 users simultaneously. DEC VAX and IBM AS/400 are commonly used mini-computers.

4. Micro-Computer

Micro-Computers are computers that are powered by microprocessors. Sometimes they are referred as SINGLE CHIP PROCESSOR a SYSTEM-ON-A-CHIP. Micro-computers or personal computers are the smallest computers, designed to be used by individuals for writing, illustrating, budgeting, playing games and communicating with other computers.

Programming Language

A programming language is a type of software. A program is a set of step by step instruction that directs the computer to do the tasks you want it to do and produce the result you want. A set of rules that provides a way of telling a computer when operations to perform is called a Programming Language.

Machine Language (Low Level Language)

Every creation of this universe has its own language. Like wise, computer has a language that is called Machine Language (machine level language) for instructing computer to perform specific task. It is also called binary language because it is the language of 0s and 1s, means every instruction in Machine language consists of a series of 0s and 1s (binary code) that a computer can understand and execute directly. Each machine language statement corresponds to one machine action. An operation that requires one machine language instruction in one computer may require several instructions in another computer. Each computer has its own unique machine language.

Assembly Language

In assembly language, the statements are written in symbolic codes (termed as mnemonics) that are easier for human to read and write as compared to machine language. Each assembly language statement corresponds to one machine language statement.

Advantages of Assembly Language

1. Operation codes of machine language are mnemonics, which are easy to remember.
2. An Assembly language program may be written easily as compared to machine language.
3. The memory addresses are used in machine language which is replaced by the variable names in this language.
4. Revision of complete program is quite easy.
5. The insertion and deletion of the instructions in the program are quite easy.

Disadvantages of Assembly Language

1. As compared to machine language assembly language is less efficient.
2. An assembly language program cannot be executed on small size computers.

High Level Language

High level languages are closer to human languages than low-level language and include statement like GOTO and PRINT which are regular words. Unlike the assembly language, the program of high level languages do not have to be written for a particular computer, but it can be execute on any machine that has a compiler for that language.


Internet is the largest network of the world that connects computers located t different parts of the world. The Internet has had a huge impact on society. The Internet provides information and service, as well as the ability to communicate to people all around the world in a variety of ways. These range from bulletin boards and chat rooms to voice conversations and video conferencing.
The Internet creates new ways for citizens to communicate, congregate and share information. It is obvious that the Internet has and will continue to change the way we live.

All in all, the Internet is affecting so many people’s lives in most welcome, exciting and challenging ways.

Advantages of Internet

1. It gives information about every field of life.
2. You may take advantages from encyclopedias and dictionaries with the help of Internet.
3. You my get information according to your need through Internet.
4. It gives a co-ordination with whole world and its interests.
5. It helps to exchange views with the person of same mental attitude.
6. Internet brings the world closer.
7. Current happening incident can be discovered by the use of Internet.
8. Any kind of topic related with politics, fashion, science etc can be discovered by use of Internet.

Disadvantages of Internet

1. The student waste their precious hours on sitting on Internet without taking any positive and constructive benefit.
2. Most of the people using Internet to satisfy their negative desires.
3. Adult material is easily available through Internet which destroys the moral values of young boys and girls.
4. Computer hacking is very common by the use of Internet some extreme minded people can digest the money through the use of credit cards of others.
5. The students waste their time in useless talking with each other.
6. Several hours on Internet without any purpose produce wrong effects on a person.


A compiler is complex system software that automatically converts a program written in some high-level language into an equivalent low-level machine language. The compiler or the language processor converts the entire program into machine code before execution. A program written by a programmer in a language other than machine language is called a Source Program. The output from a compiler or an assembler, which consists of machine language instructions, is called the Object Program.


An interpreter is another type of translator that converts each statement of a program written in a high level language into machine code and executes it before translating the next statement of the source program. It differs from a compiler that translates the entire source program into object program without undergoing its execution.

Short Notes

BASIC – Beginner’s All-Purpose Symbolic Instruction Code)

John Kemeny and Thomas Kurtz developed BASIC in 1964 for beginners. BASIC is a very simple language to use and understand. It uses simple English words. Even a person with a little knowledge of computer programming can learn it and utilize it for business and scientific purpose. It is a powerful language that has grasped millions of users. The biggest problem with it is that it has no standard version and different manufacturers modified it into different versions.


A French mathematician Blaise Pascal introduced a programming language by the name of PASCAL. It is a highly structured programming language. It was developed in 1970’s after the concept of structured programming.

FORTRAN (Formula Translation)

It was developed in 1957 for IBM computers to solve mathematical, scientific and engineering problems. It was one of the first languages to introduce the concept of “Modular Programming”. It has been revised so many times.

Advantages and Disadvantages of Computers

Following are some advantages and disadvantages of computer in our life.


1. Computers make us more productive in many of our jobs.
2. In education they can help us for better understanding faster learning and broaden our thinking.
3. In hospitals we have better diagnosis, proper treatment and better healthcare.
4. In business, they are used to record stocks of raw materials as well as finished products, making customer’s bill, analyzing sales of various products etc.
5. In banks, they are used for day-to-day processing of customer’s accounts and payments.
6. In manufacturing, they provide ways to develop a representation of the product and to test it in a variety of simulated environments.


1. Unemployment due to automation.
2. Wastage of time and energy in useless computer activities.
3. Data security.
4. Privacy
5. Computer Crimes.


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