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Tuesday, 13 December 2016



Generations Of Computer
Image credits: Wikipedia

Over the past five decades, computers have gone through five generations of development. Good features of the earlier generations have been passed to the later generation. A short description of various computer generations is given below.

First Generation (1942-1955):

  • Vacuum tubes as CPU components.
  • Mercury delay lines, Electrostatic (CRT) for memory.
  • Machine or Assembly language programming.
  • Fixed-point arithmetic was used.
  • Magnetic tape/magnetic drum as secondary memory.
  • No concept of operating system.
  • Punched card and Paper tape to feed program and data and to get results.

Examples: ENIAC (first electronic, computer completed in 1946), used vacuum tubes as CPU components and memory. Stored program concept in 1946 made programs and data to be stored in separate memories.
Other examples are  EDVAC (1951), EDSAC (1949), UNIVAC (1951),  IBM’s 701(1953), IBM 704(1955), IBM 709.

Second Generation (1955 to 1964):

  • Transistors in place of vacuum tubes in CPU, and other electronic components.
  • Magnetic ferrite-core memory as main memory, random-access non-volatile memory.
  • Machine independent high-level languages like FORTAN, COBOL, and ALGOL were developed and used as programming languages.
  • Floating point arithmetic was used.
  • I/O processors were introduced to supervise and control input/output operations. They relieved CPU from many time-consuming routine works.
  • System Software like complies, subroutines etc. were introduced.
  • Bach processing was introduced.
  • Punched cards continued during this period also.
  • Computers were made effective in industry and commercial organizations: payroll, inventory control, marketing, production planning, general ledger system and research.

Examples : IBM 1620 (1960), IBM 7090 (1960) , IBM 7094 (1962). Digital Data Corporation’s (DEC’s): (Programmed Data Processor) PDP 1 (1957), PDP 5 (1963), PDP 8 (1965), Control Data Corporation’s (CDC’s) CDC 1604.

Third Generation (1964-1975):

  • ICs(SSI and MSI) started replacing transistors in CPU, I/O processors.
  • Semiconductor memories (RAM and ROM’s) using LSI technology replaced magnetic core type main memory.
  • Certain new techniques such as parallel processing (Multiprocessing), Multiprogramming, Multi-user (time sharing); to increase the effective speed of program execution.
  • Cache memory was also introduced.
  • Operating systems for multiprogramming and time shared systems (multi-user systems) were developed.
  • Computers were widely applicable to multi-user applications, on-line systems: airline reservations, interactive query system automatic industrial control.

Examples: CDC 7600 (1969), IBM 370 series (1970), PDP 11 (1970,16-bit computer), CDC’s CYBER -175 and STAR-100. Intel’s 4004,8008,8080.

Fourth Generation (1975-1989):

  • Use of microprocessor as CPU. Earlier, Cache, MMU (Memory Management Unit), FPU (Floating Point Unit i.e. math processor) were on separate ICs. Now-a-days all such components and CPU are packed into a single IC of the microprocessor.
  • Computer network is being-widely used: LAN(Local Area Network), MAN (Metropolitan Area Network), WAN (Wide Area Network).
  • Multifunction peripheral chips providing functions of interrupt controller, DMA controller, Bus controller, Memory refresh controller etc on a single IC have been developed.
  • Disk drives of gigabytes capacity, as secondary memory.
  • CD-ROMs, DVD-ROMs have been developed as read only memory for storage.
  • Database management: dbase, Sybase, FoxPro, Oracle.
  • ES (Expert System) using AI (Artificial Intelligence).
  • Today computers are widely used in industrial control, instrumentation, consumer appliances, banking services, officers, military equipment, education, communication, games, analysis and design, research work and so forth.

Examples: 8085,8086,8088,80286,808386,80486, Pentium Pro, P-II,P-III,P-IV, Celeron, all by Intel corporations Ltd. Motorola’s 6809,68000,68040. Power PC. DEC’s Alpha, MIPS, SUNS’s ULTRA SPARC, AMD’s, K-6,K-7.

Fifth Generation Computers (~):

The fifth generation computers are expected in the near future. Main features of these computers will be as follows:

  • Computers will use ULSI (Ultra Large Scale Integration)
  • Some important functional chips like Cache controller, advanced interrupt controller will exist.
  • Computers will use extensive parallel processing such as multiprocessor system and concurrent logic programming.
  • Natural languages will be used as source languages i.e., programmer will give commands in English or any other languages.
  • Intelligent programming will be used where programmer will tell the computer what to do, rather than how to do. Intelligent software will be used for this purpose. 
  • Languages like PROLOG will also be widely used.
  • Artificial intelligence and full automation will be the central theme.

Programming Generations

In terms of Programming Languages and software, the generations of software are:
  • First generation: Machine language.
  • Second generation: Low-level programming languages such as Assembly language.
  • Third generation: Structured high-level programming languages such as C, COBOL and FORTRAN.
  • Fourth generation: Domain-specific high-level programming languages such as SQL (for database access) and TeX (for text formatting)



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