Question

differences between first to fourth generations of computer

Answer 1

The First Generation lasted from 1946--1952.It used Vacuum tubes.
The Fourth Generation lasted from 1971-1990 and used large scale Integrated circuits and Microprocessor Chip.

Answer 2

the first generation computers used vacuum tubes and had gigantic brain chips,

the forth generation comps are smaller , less clumsier and have small microprocessors, but bigger memory.