Computer Generation: The ENIAC (Electronic Numeric Integrater and Calculater), EDSAC (Electronic Delay Storage Automatic Calculator), UNIVAC-I (Universal Automatic Computer) were known as First Generation computers. They were slow, used Vacuum Tubes and high power, large space to house and had limited programming capability.
The second generation started arriving in 1959. It used solid state components like Transisters developed by Bell Laboratories in 1947, was smaller in size faster and had greater computing capabilities and used high-level programming languages. It transacted either scientific/non-scientific applications, not both.
IBM's System/360 family of Mainframe Computers in 1964 could do both scientific and non-scientific applications. These were Third Generation Computers. In this the processing were provided at a central place.
The development of Mini-computers by Digital Equipment Corporation (DEC) in 1965 filled the gap left by bigger, faster centralized approach of Mainframe Computers Timesharing, a term used to describe an independent processing system, was slow, but could be used from different stations. The user has direct access to a central processor giving him a feeling that the computer is exclusive for him. This was developed by John Kemeny and Thomas Kurtz. Later a microprocessor with circuits need to perform arithemetic-logic and control functions was developed for use in PCs. The circuit in this processor is built on a single silicon chip.
The Japanese call their fifth generation computers that are being produced as Knowledge Information Processing System (KIPS).