Friday, July 6, 2018

Different Types & Generations of Computers with Advantages & Disadvantages (notes)

The very simple definition of Computer is, " It is electronic device which is used for storing the data & processing the data by using binary numbers. User can provide multiple instructions of performing specific tasks under specific conditions. As per user requirements, there are three main types of computer and five generations of computers.


Due to different behavior of computer we can divide it in three types according to it

Analog Computers
Digital Computers
Hybrid Computers

Analog Computers

  • Analog computers show the continuity of specified value means, which are used to measure continuous values.
  • Analog computers operate by measuring rather than counting.
  • An examples are analog clock, thermometer.

Digital Computers

  • Digital computers based on the rule of counting. These directly count numbers.
  • In fact digital computers used signals, which can distinguish between just two values 0 and 1.
  • Digital watches are the example of digital computers.
  • Desktop computers and Laptop are also the examples of digital computers.

Hybrid Computers

  • The combination of Analog and Digital computer is called Hybrid.
  • These are better and widely in used.
  • A part of processing is done on analog and a part of processing is done on digital computer.
  • An example of Hybrid computer system is a cement plant where all calculations are made by digital computers and action such as increase/ decrease in certain material by analog computer.

Computer technology changed with time, the very first generation computer was designed back in 1950 and it kept improving time to time. 5 Different Computer generations and further developments are mad with time.


First Generation Computers (1942-1955)
Second Generation Computers (1955-1964)
Third Generation Computers (1964-1975)
Fourth Generation Computers (since 1971)
Fifth Generation Computers (Present- Beyond)


  • The vacuum tube technology was used in first generation computers.
  • MARK-1, ENIAC, EDVAC, UNIVAC-1 etc machines belong to the first generation of computers.


  • Vacuum tubes were only electronic components available during those days.
  • Vacuum tube technology made possible the advent of that time.
  • They could perform computations in milliseconds.


  • Too bulky (large) in size.
  • Unreliable.
  • Air-conditioning required.
  • Thousand of vacuum tubes were used to produce large amount of heat and burnt out frequent.
  • Not portable.


  • The transistor technology was used in second generation.
  • It was invented in 1948 at Bell laboratories.
  • The transistor is smaller in size and more reliable than vacuum tube.


  • Smaller in size as compared to first generation computers.
  • More reliable.
  • Less heat generated.
  • These computers were able to reduce computational times from milliseconds (10-3) to microseconds (10-6).
  • Better portability.


  • Air conditioning required.
  • Commercial production was difficult and costly.
  • Frequent maintenance required


  • The IC (integrated Circuits) technology was used in third-generation.
  • It is small in size (upto 5mm square).
  • A circuit having large number of electronic components like transistors, capacitors etc.


  • Maintenance cost was low because failure rate of hardware was very low.
  • Portable and more reliable.
  • Easily movable.
  • Less power requirement than previous generation computers.
  • Commercial production was easier and cheaper.


  • Air conditioning required in many cases.
  • Highly difficult technology required for the manufacture of IC chips.


  • The microchip technology was introduced in this generation. With the advancement in IC technology, LSI (large Scale Integration) chips were developed.
  • After LSI, the VLSI (very large scale Integration) was developed and made the development possible. 
  • Using VLSI technology the entire CPU is designed on a single silicon chip.


  • Smallest in size because of high components density.
  • Very reliable.
  • Heat generation is low.
  • Large memory.
  • Portable and reliable.
  • Cheapest among all generations.


  • Highly difficult technology is required for the manufacturing of microprocessor chip.
  • Fifth Generation Computers (Present- Beyond)
  • Having their own thinking power.
  • Making decisions themselves.
  • Having capabilities of learning.
  • ULSIC (Ultra Large Scale Integrated Circuits) technology.
  • Artificial Intelligence

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