Answer:
In the Second generation of Computers Transistors were used they were small in size cheaper then vacuum tubes and reliable plus they also generated lot of heat and there was a need of A/C required and also that they also consumed lot of Electricity. also Only Machine Language was used. time period (1959-1965)
4th generation of Computers Microprocessor was used which is used till now( present -day today)
.they were reilable
.cheap
.consumed less electricity
.small in size
. not generated lot heat
.no A/C required
. Assembly and machine language was used.