The computer as we see it today is a result of extensive research and development through the decades. The brief history of its evolution are outlined below..

There are totally five computer generations known till date. Each generation has been discussed in detail along with their time period and characteristics. Here approximate dates against each generations have been mentioned which are normally accepted.

First generation: 1946-1959 [Vacuum tube based]: First-generation computers used vacuum tubes and values as their basic electronic component. They were extremely large in size and electricity consuming . The language used for storing and processing data was machine language. Some of the first-generation computers are: ENIAC (electronic numerical integrator and calculator) – it was built in 1946 at the university of PENNSYLVANIA, U S A by JOHN ECKERT and JOHN MAUCHLY.

Second generation:1959-1965 [Transistor based]: In the generation of computers, transistors were used in place of vacuum tubes. Transistors are more compact than vacuum tubes as they are made up of semiconductors. They are also more durable than vacuum tubes. Programming languages some of the computers of the second generation are: IBM 1620 – Its size was used smaller as compared to the first-generation computers and it was used mostly for scientific purpose. IBM 1401- IT was used for was business application. CDC 3600- IT was used for scientific purpose.

Third generation:1965-1971 [Integrated Circuit based]: In the third generation of computers integrated circuits (ICs) began to be used. These ICs were called chips. These ICs are more compact than a transistor. Single ICs has many transistors, registers and capacitors, placed on a single thin of silicon. So the computer built of such components became smaller. Some of the computers developed during this period were :  IBM- 360- Developed by IBM in 1964.  PDP – 8 -Developed by DEC in 1965.

Forth generation:1971-1980 [VLSI microprocessor based]: The computers of fourth generation used Very Large Scale Integrated (VLSI) circuits. VLSI circuits having about 5000 transistors and other circuit elements and their associated circuits on a single chip made it possible to have microcomputers of fourth generation. Fourth generation computers became more powerful, compact, reliable, and affordable. As a result, it gave rise to personal computer (PC) revolution. In this generation time sharing, real time, networks, distributed operating system were used. All the high-level languages like C, C++, DBASE etc., were used in this generation.Some of the computers developed during this period are DEC 10.  STAR 1000  PDP 11  CRAY-1(Super Computer)  CRAY-X-MP(Super Computer)

Fifth generation:1980-onwards. [ULSI microprocessor based]: In the fifth generation, the VLSI technology became ULSI (Ultra Large Scale Integration) technology, resulting in the production of microprocessor chips having ten million electronic components. This generation is based on parallel processing hardware and AI (Artificial Intelligence) software. AI is an emerging branch in computer science, which interprets means and method of making computers think like human beings. All the high-level languages like C and C++, Java, .Net etc., are used in this generation.