This document discusses the history and development of computers over five periods from 1946 to the present:
1. The first period from 1946-1957 saw the introduction of early electronic computers like ENIAC and UNIVAC I that used vacuum tubes.
2. The second period from 1958-1964 was marked by the development of transistors which made computers smaller, faster, and more reliable. IBM introduced popular models like the IBM 1620.
3. During the third period from 1965-1969, integrated circuits were developed which packed many components onto a small chip, leading to much faster microsecond processing speeds. Popular models included the IBM 360.