In the beginning, there were no computers. To add or subtract , man used his fingers and toes. An abacus is known to be the first mechanical calculating device. The main purpose of the abacus was that additions and subtraction could be performed quickly. The abacus was developed by the Egyptians in the 10th century B.C, but the final structure was given in the 12th century A.D. by the Chinese educationists. Abacus is made up of a frame in which rods are fitted across with rounds beads sliding on the rod.


Napier’s Bones is an Abacus invented by John Napier. Napier’s used the bone rods for counting purpose where numbers were printed on them. With the help of these rods ,one could do addition, subtraction, multiplication and division speediy.

Pascal’s calculator

In the year 1642, Blaise Pascal a French scientist invented an adding machine called Pascal’s calculator (Pascaline), which represents the position of digit with the help of gears in it. Though these machines were early forerunners to computer engineering, the calculator failed to be a great commercial success.

Leibniz Calculator

Leibniz was successfully introduced as a calculator onto the market in the year 1646. It was designed further in 1673 but it took until 1694 to complete. The calculator could perform the basic mathematical operations such as add, subtract, multiply, and divide. Wheels were placed at right angles which could be displaced by a special stepping mechanism.

Analytical Engine

This analytical engine, the first fully-automatic calculating machine, was constructed by British computing pioneer Charles Babbage (1791-1871), who first conceived the idea of an advanced calculating machine to calculate and print mathematical tables in 1812. This Analytical Engine incorporated an arithmetic logic unit, control flow in the form of conditional branching and loops, and integrated memory, making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete.

Five Generations of Computers

First Generation of Computers (1942-1955)

The beginning of commercial computer age is from UNIVAC (Universal Automatic Computer). The first generation computers were used during 1942-1955. They were based on vacuum tubes. Examples of first generation computers are ENIVAC and UNIVAC-1.

Advantages :

  • Vacuum tubes were the only electronic component available during those days.
  • Vacuum tube technology made it possible to make electronic digital computers.
  • These computers could calculate data in milliseconds.
Disadvantages :
  • The computers were very large in size.
  • They consumed a large amount of energy.
  • Non-portable.
  • Limited commercial use.
  • Very slow speed.
  • Used machine language only.
  • Used magnetic drums which provide very less data storage.

Second Generation Computers (1955-1964)

The second generation computers used transistors. The size of the computers was decreased by replacing vacuum tubes with transistors. The examples of second generation computers are IBM 7094 series, IBM 1400 series and CDC 164 etc.

Advantages :

  • Smaller in size as compared to the first generation computers.
  • Used less energy and were not heated.
  • Better speed and could calculate data in microseconds
  • Used faster peripherals like tape drives, magnetic disks, printer etc.
  • Used Assembly language instead of Machine language.Disadvantages :
  • Cooling system was required
  • Constant maintenance was required
  • Only used for specific purposes
  • Costly and not versatile

Third Generation Computers (1964-1975)

The Third generation computers used integrated circuits (IC). The first IC was invented and used in 1961. The size of an IC is about 1⁄4 square inch. A single IC chip may contain thousands of transistors. The computer became smaller in size, faster, more reliable and less expensive. The examples of third generation computers are IBM 370, IBM System/360, UNIVAC 1108 and UNIVAC AC 9000 etc.

An integrated circuit (IC), sometimes called a chip or microchip, is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated.

Advantages :

  • Smaller in size as compared to previous generations.
  • More reliable.
  • Used less energy.
  • Better speed and could calculate data in nanoseconds.
Disadvantages :
  • Air conditioning was required.
  • Highly sophisticated technology required for the manufacturing of IC chips.

Fourth Generation Computers (1975-Present)

The fourth generation computers started with the invention of the microprocessor. The Microprocessor contains thousands of integrated circuits. When the LSI (Large Scale Integration) circuit and VLSI (Very Large Scale Integration) circuit was designed, it greatly reduced the size of computer. The size of modern Microprocessors is usually one square inch. It can contain millions of electronic circuits. The examples of fourth generation computers are Apple Macintosh & IBM PC.

Advantages :

  • More powerful and reliable than previous generations.
  • Small in size
  • Fast processing power with less power consumption
  • Fan for heat discharging and thus to keep cold.
  • Cheapest among all generations
  • All types of High level languages can be used in this type of computers
Disadvantages :
  • The latest technology is required for manufacturing of Microprocessors.

Fifth Generation Computers (Present & Beyond)

Scientists are working hard on the 5th generation computers with quite a few breakthroughs. They are based on the technique of Artificial Intelligence (AI). Computers can understand spoken words & imitate human reasoning. The IBM Watson computer is one example that outsmarts Harvard University Students.