Computer Science Class 6 Chapter-1 Evolution of Computers

 Overview of the chapter

  • Different generations of computers
  • First Generation: 1946-1958 (Vacuum Tubes)
  • Second generation: 1959-1964 (Transistors)
  • Third generation: 1965-1970 (Integrated Circuits IC)
  • Fourth generation: 1971- today (Microprocessors)
  • Categories of computers
    • On the basis of working principle
    • On the basis of size
    • On the basis of brand


  • Computer are such an integral part of our everyday life.
  • Computer is an electronic machine which performs mathematics and logical calculations.
  • Charles Babbage is called the Father of computer.
  • Now, in this chapter, we are trying to describe the types of computers and elaborate classification of computer.
  • Computers can be classified in various ways depending on their generation, working, size and use.

Generations of Computer

  • The term ‘Generations’ means improvement in the development of a product (computer).
  • Every new generation, the circuitry has gotten smaller and more advances than the previous generation.
  • New discoveries are constantly being developed that effect the way of we live, work and play.

The first generation: 1946- 1958 (Vacuum Tubes)

  • The Ist generation computers were huge, slow, expansive and often unreliable.
  • In 1946 two Americans, Presper Eckert and John Mauchly built the ENIAC.
  • ENIAC was made up of 18,000 vacuum tubes and occupied a 30 * 50 feet room.
  • ENIAC stands for Electronic Numeric Integration and Calculator.

Key Features

  • Vacuum tubes based, punched tape input or output, about 1,000 circuits per cubic foot.

Examples- ENIAC, IBM models 604,650(drum memory), 701,702,704,705,709 etc.

Things to remember:
ENIAC was the world’s Ist successful electronic computer.


The Second generation: 1959-1964 (Transistors)

  • As the development moved further, the second generation computer knocked the door.
  • In 1947, three scientists, John Bardeen William Shockley and Walter Brattain working at AT & T’s Bell Labs invented transistor.
  • It was faster, more reliable, smaller & much cheaper to build than a vacuum.
  • One transistor replaced the equivalents of 40 vacuum tubes.
  • The size of computer also decreased and it became much smaller than that of earlier computer.
  • Therefore, they were very cheap to produce.

Key Features

  • Low electricity consumption.
  • Mare reliable and faster.
  • Used transistors, about 1,00,000 circuits per foot.

Examples – UNIVAC – III, IBM 7070, 7080,7090,1400,1600 series etc…

Third generation: 1965-1970 (Integrated Circuits IC)

  • Invented in the year 1965.
  • In this generation of computer, IC (Integrated Circuits) was used as the electronic component for computers.
  • The development of IC gave birth to a new felid of microelectronics.
  • It is small in size, superior performance and reliability than the previous circuits.
  • Robert Noyce of Fairchild Corporation & Jack Kilby of Texas Instruments discovered the integrated circuits.

Key Features

  • Low power consumption.
  • Large scale IC, 10 million circuits per square foot.

Examples – IBM 360 series, GE 235 etc…

The Fourth generation: 1971- today (Microprocessors)

  • This is the generation where we are working today. The computers which we see around us belong to the fourth generation computers.
  • By putting millions of transistors onto one single chip more calculation and faster speeds could be reaches by computers.
  • Ted Hoff, employed by Intel invented a chip.
  • The size of a pencil eraser that could so all the computing and logic of a computer.
  •  It is evident that he next generation of computer i.e. fifth generation will be developed soon.
  • In that generation, computer will possess artificial intelligence and it would be able to take self-decisions like a human beings.

Key Features

  • Very large scale integration billions of circuits per cubic foot.
  • Portable computer developed.
Things to remember:
Supercomputers can execute a single program faster than a mainframe.

Examples– IBM system 3090, HP 9,000 etc…


Analog computer

  An analog computer is a computer that represents data by measurable quantities, as voltages than by expressing the data as numbers.

Example- Thermometer, speedometer, petrol pump indicator, multimeter etc.


Digital computer

 A digital computer is the most commonly used type of computer and is used to process information with quantities using digits, usually using the binary number system.

Hybrid (analog + digital) computer

 A combination of computers those are capable of inputting and outputting in both digital and analog signals. A hybrid computer system setup offers a cost effective method of performing complex simulations.

On the basis of size


A supercomputer is a computer that performs at or near the currently highest operational rate for computers.

It is mainly used for scientific and engineering applications that must handle very large databases or do a great amount of computation.

For example, weather forecasting requires a supercomputer.

Mainframe computer

It is very large and expensive computer capable of supporting 100 or even 1,000 of users at a time.

Mini computer

A computer with processing and storage capabilities smaller than those of mainframe but larger than those microcomputer.

On the basis of Brand

IBM computers

It refers to a family of personal computers by IBM.

Apple/Macintosh computer

It is also known a Mac, is a line of personal computers (PC’s) designed, developed, and marketed by Apple Inc.

Let Us Summaries

  • Charles Babbage is called the ‘Father of computer’.
  • The first generation computer were huge, slow, expensive and often undependable.
  • One transistor replaced the equivalent of 40 vacuum tube.
  • Integrated circuit were used as the electronic component for computer.
  • The microprocessor led toward the invention of personal computer or microcomputers.
  • Digital computer processes information with quantities using digit usually using the binary number system.
  • Hybrid computer is a combination of computer those are capable of inputting and outputting in both digital and analog signals.
  • Supercomputer perform at or near the currently highest operational rate for computers.
  • A minicomputer is a multiprocessing system capable of supporting from 4 to about 200 users simultaneously.
  • Desktop Computer is personal or micro-mini computer sufficient to fit on a desk.
  • Laptop is a portable computer complete with an integrated screen and keyboard.
  • Palmtops have no keyboard but the screen serves both as an input and output device.

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This Post Has 2 Comments

  1. Suraj verma

    I am so happy because It is very helpful,

  2. Suraj verma

    I am so happy😊 it is very helpful

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