History and generation of computer
               Computer was developed as a counting machine at
very fast . At initial stage it is used for                     accounting and data manipulation .
               The earliest computing device was developed 450
BC , it called Abacus .
              The first desktop calculating machine was
developed as early as 1642 .
       It can perform  arithmetic operations . This
machine could perform only 2 basic operations                  additions and subtractions .
       Next a German mathematician developed pascal ‘
calculator for performing plus , minus ,                    into , divide
            Charles Babbage designed the modern computer in
the year 1822 . He is called father of computer .
             The first electronic computer ENIAC (Electronic
Numerical Integrator and Calculator) was                 designed in 1946 . It can perform 5000
calculations per second .
      After ENIAC an electronic computer was developed
in 1949 . It is called EDVAC (Electronic             Discrete Variable Automatic Computer)   
         
  The developments of computers has followed different
technology , and these stage of technical         differences called generations .
1st generation (1945-1960)
1st generation of computer was vacuum tubes. In
this computer 18000 vacuum tubes & 60000 switches are used . It is very
large in size and required large space. It has small memory and no secondary storage.
2nd generation (1960-1965)
In this generation transistors are used in place of vacuum
tubes . Magnetic core is used for memory storage . The size of transistor is
much smaller than vacuum tubes and very faster and reliable . The major
advantages of transistor was small size and less power consumption . The cost
of transistor is very less than vacuum tubes .
3rd generation (1965-1975)
In this generation silicon chips are used . These computer
used Integrated Circuit (IC) of silicon chips in place of transistors . By
using IC the size of computers , cost , heat generation and power consumption
decrease to a great extent .These machine used IC ‘s with LSI (Large Scale
Integration)
4th generation (1975)
These computers used IC’s with VLSI  (Very Large Scale Integration) . These
computers have high processing speed , very low maintenance and power
consumption . 
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