Classification of Computer on the Basis of Generation

The evolution of digital computing is often divided into generations. Each generation is characterized by dramatic improvements over the previous generation in the technology used to build computers, the internal organization of computer systems, and programming languages. Although not usually associated with computer generations, there has been a steady improvement in algorithms, including algorithms used in computational science. The following history has been organized using these widely recognized generations as mileposts.


First Generation (1937-1953)

first Generation computer

The main characteristics of this generation of computers were – 

  • Used vacuum tubes in circuit, like diodes, triodes, etc and magnetic drums for the memory.
  • Were very bulky in size, height and occupied large spaces.
  • Long start-up time (tubes had to be heated).
  • Had high failure rate and short life.
  • Had limited memory.
  • High power consumption.
  • Low speed (to the order of milliseconds).
  • Examples of First Generation computers are—ENIAC, EDVAC, UNIVAC etc.

Second Generation (1954-1962)

second generation computer

Transistors and printed circuit boards replaced valves in the second generation of computers. They also replaced the magnetic drum memory by the magnetic core memory. Characteristics are given below :-

  • Facts based or Information based.
  • Considerable reduction in the physical size.
  • Increased reliability. Lower power consumption. Lower heat production.
  • Low failure rate.
  • Larger memory and greater speed (milliseconds to microseconds).
  • Transistors as basic components.
  • Faster and better I/O peripherals.
  • Developments of languages like COBOL, FORTRAN, ALGOL etc.
  • Examples of second-generation computers are-IBM-1401, Honewell-800, IBM-1620, IBM-7000, ICL-1901 etc.

Third Generation (1963-1972)

Third Generation computer

Third generation computers appeared with integrated circuits. Various new concepts in data processing like batch processing, real time system, time-sharing system, multiprogramming system etc., were introduced. The characteristics of the third generation computers are given below:

  • Replacement of transistor by IC on the circuit boards.
  • Tremendous reduction in size.
  • Reduction in processing times to nanoseconds.
  • Efficient use of CPU and I/O devices.
  • Random access and mass storage.
  • Used programming language like BCPL, CPL, and UNIX operating system.
  • Modular design of computers.
  • Larger memory.
  • Examples of third generation computer are—IBM-360 series, ICI-1900, IBM-370 series, CDC-7600 series etc.

Fourth Generation (1972-1984)

Fourth Generation computer

This generation began after the development of Large Scale Integrated Circuits (LSI) and Very Large Scale Integrated Circuits (VLSD). Characteristics of this generation are given below:

  • Semiconductor memory instead of core memory.
  • Introduction of Micro Programmed Logic.
  • Usage of powerful operating systems, virtual memory concepts that enable a programmer to write programs requiring more memory than the available memory.
  • Increased storage capacity and speed.
  • High-speed vector processor.
  • Many powerful and user-friendly high level languages like, C, Pascal etc.) and operating systems introduced.
  • For example, ICL-2903 (from International Computer Limited), CD-1700 (from Controlled Data Corporation), CRAY-1, CRAY X-MP, CYBER 205 etc.

Fifth Generation (1985-1990)

Fifth Generation computer

The development of the next generation of computer systems is characterized mainly by the acceptance of parallel processing. Until this time parallelism was limited to pipelining and vector processing, or at most to a few processors sharing jobs. The fifth generation saw the introduction of machines with hundreds of processors that could all be working on different parts of a single program. The scales of integration in semiconductors continued at an incredible pace-by 1990 it was possible to build chips with a million components and semiconductor memories became standard on all computers. Other new developments were the widespread use of computer networks and the increasing use of single-user workstations. Prior to 1985 large scale parallel processing was viewed as a research goal, but two systems introduced around this time are typical of the first commercial products to be based on parallel processing.

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The Sequent Balance 8000 connected up to 20 processors to a single shared memory module (but each processor had its own local cache). The machine was designed to compete with the DEC CAX-780 as a general purpose Unix system, with each processor working on a different user’s job. However, Sequent provided a library of subroutines that would allow programmers to write programs that would use more than one processor, and the machine was widely used to explore parallel algorithms and programming techniques.

The Intel iPSC-1, nicknamed “the hypercube”, took a different approach. Instead of using one memory module, Intel connected each processor to its own memory and used a network interface to connect processors. This distributed memory architecture meant memory was no longer a bottleneck and large systems (using more processors) could be built. The largest iPSC-1 had 128 processors.

Towards the end of this period a third type of parallel processor was introduced to the market. In this style of machine, known as a data-parallel or SIMD, there are several thousand very simple processors. All processors work under the direction of a single control unit; i.e., if the control unit say “add A to B” then all processors find their local copy of A and Add it to their local copy of B. Machines in this class include the Connection Machine from Thinking Machines, Inc., and the MP-1 from Maspar, Inc. Scientific computing in this period was still dominated by vector processing.

Most manufacturers of vector processors introduced parallel models, but there were very few (two to eight) processors in these parallel machines. In the area of computer networking, both wide area network (WAN) and local area network (LAN) technology developed at a rapid pace, stimulating a transition from the traditional mainframe computing environment towards a distributed computing environment in which each user has their own workstation for relatively simple tasks (editing and compiling programs, reading mail) but sharing large, expensive resources such as file servers and supercomputers. RISC technology (a style of internal organization of the CPU ) an plummeting costs for RAM brought tremendous gains in computational power of relatively low cost workstations and servers. This period also saw a marked increase in both the quality and quantity of scientific visulization. 

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Updated: July 2, 2019 — 8:48 am

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