First Generation Computers (1940-1956):
They used vacuum tube technology.
Vacuum tubes produce lot of heat and needs to be cooled with A.C.
Their examples were ENIAC, UNIVAC-I, IBM-604, Mark-I and EDSAC etc.
This generation computers had following drawbacks:
a) Very big in size
b) Slow in speed and have less memory
c) Large power consumption
d) Difficult maintenance.
Second Generation Computers (1956-1963):
They used transistors instead of vacuum tubes.
They are reliable and cheaper.
They used punch card readers, magnetic tapes and printers.
They use assembly language.
High level programming languages were introduced like FORTRAN and
COBOL in these computers.
Their examples were UNIVAC-II, IBM 7030, 7780 and 7090, NCR 300 etc.
Third Generation Computers (1963-1971):
They used Integrated circuits consisting of transistors, diode and resistances.
These computers were smaller and consume very less power.
These computers used more versatile programs like real time programming.
They can run different applications at the same time.
Their examples were Burroughs 6700, IBM System / 360, System 3 and
Control Data Corporations 3300 and 6600.
Fourth Generation Computers (1971-Till Now):
They use LSI (Large Scale Integration) and VLSI (Very Large Scale
Integration) chips.
Microprocessors were also developed in fourth generation.
They are very fast and have large memory capacity.
Large variety of softwares are present in these computers.
They support multimedia software that combine text, image, sound and
videos.
They use modern languages like C, C++, Java etc.
Their examples are Pentium Series, Dual Core, Core i3, i5 and i7 etc.
Fifth Generation Computers (Upcoming):
This generation is currently under process.
Scientists are trying to design such machine which can think and understand
natural languages.
They will be based on Artificial Intelligence.
Their examples will be robots and expert systems.