Nov 24, 2012


INTRODUCTION: The first electronic computer was designed and built at the university of Pennsylvania based on vacuum tube technology.

Vacuum tubes were used to perform logic operations and to store data. Generations of computers has been divided into five according to the development of technologies used to fabricate the processors, memories and I/O units.


Example- ENIAC = Electronic Numerical Integrator and Calculator.
               EDSAC = Electronic Delay Storage Automatic Calculator.
               EDVAC = Electronic Discrete Variable Automatic              Computer.
              UNIVAC = Universal Automatic Computer IBM 701.
              IBM-650 etc.

Technology used:  Vacuum tube.


1. Vacuum tubes were used- basic arithmetic operations took few milliseconds.
2. Bulky
3. Consume more power with limited performance.
4. High cost.               
5. Uses assembly language- to prepare programs. These were translated into machine level language for execution.
6. Mercury delay line memories and electrostatic memories were used.
7. Fixed point arithmetic was used.
8. 100 to 1000 fold increase in speed relative to the earlier mechanical and relay based electromechanical technology.
9. Punched cards and paper tape were invented to feed programs and data and to get results.
10. Magnetic tape/magnetic drum were used as secondary memory.
11. Mainly used for scientific computations


1. Only vacuum tubes are required.


1. Generates heat.
2. Airconditioning required.
3. Large in size.
4. Unreliable.
5. Constant maintenance required.


Example-IBM 7030 , Digital Data Corporation's PDP 1/5/8 , Honeywell 400. CDC-1604, CDC-3600, UNIVAC-1108 etc.

Technology used:  Transistor.


1. Transistors were used in place of vacuum tubes.
2. Small in size                                                                                3. Lesser power consumption and better performance.
4. Lower cost.
5. Magnetic ferrite  core memories were used as main memory which is a random-access nonvolatile memory.
6. Magnetic tapes and magnetic disks were used as secondary memory.
7. Hardware for floating point arithmetic operations was developed.
8. Index registers were introduced which increased flexibility of programming.
9. High level languages such as FORTRAN , COBOL etc. Were used- compilers were developed to translate the high-level program into corresponding assembly language program which was then translated into machine language.
10. Separate input-output processors were developed that could operate in parallel with CPU.
11. Punched cards continued during this period also.
12. 1000 fold increase in speed.
13. Increasingly used in business, industry and commercial organizations for preparation of payroll , inventory control , marketing , production planning , research , scientific and engineering analysis and design etc. 


1. Less heat generation.
2. Smaller in size compared to first generation.
3. More reliable.
4. Faster in action.


1. Airconditioning required.
2. Maintenance required.


Example- System 360 Mainframe from IBM, PDP-8 Minicomputer from Digital Equipment Corporation, Honeywell-6000 series, TDC-316 etc.

Technology used:  Integrated Circuit(IC).


1. ICs were used.
2. Small scale integration and medium scale integration technology were implemented in CPU, I/O processors etc.
3. Smaller and better performance.
4. Comparatively lesser cost.
5. Faster processors.
6. In the beginning magnetic core memories were used. Later they were replaced by semiconductors memories.
7. Introduced microprogramming.
8. Microprogramming , parallel processing , multiprogramming , multi-user system etc were introduced.
9. Operating system software were introduced .
10. Cache and virtual memories were introduced .
11. High level languages were standardized by ANSI. Example- ANSI FORTRAN, ANSI COBOL etc.
12. Database management , multi-user application , online systems like closed loop process control , airline reservation , interactive query systems , automatic industrial control etc emerged during this period.


1. Smaller in size.
2. Lower heat generation.
3. Less power requirement.
4. More reliable than first and second generation.
5. Faster than first and second generation.
6. Low maintenance cost.
7. Easily portable.
8. Cheaper commercial production.


1. Manufacturing difficulty.
2. Airconditioning required.


Example- Intel's 8088, 80286, 80386, 80486..... , Motorola's 68000, 68030, 68040 , Apple 2 , CRAY 1/2/X/MP, DEC-10, STAT-1000, PDP-11 etc.

Technology used:  Large and very large scale integrated circuit(LSIC and VLSIC).


1. Microprocessors were introduced as CPU- complete processors and large section of main memory could be implemented in a single chip.
2. Tens of thousands of transistors can be placed in a single chip.
3. CRT screen , laser and ink jet printers , scanners etc were developed.   
4. Semiconductor memory chips were used as the main memory.
5. Secondary memory was composed of hard disks- floppy disks and magnetic tapes were used for backup memory.
6. Parallelism , pipelining cache memory and virtual memory were applied in a better way.
7. LAN and WANS were developed .
8. Introduced C language and Unix OS.
9. Introduced graphical user interface.
10. Less power consumption .
11. High performance , lower cost and very compact
12. Much increase in the speed of operation.


1. Smaller in size.
2. Portable.
3. No airconditioning required.
4. Practically maintenance free.
5. Cheaper and reliable.
6. Less power requirement.
7. General purpose and much more cheaper.


1. Complex software.
2. Highly sophisticated technology required for manufacturing LSIC and VLSI chips.


Example- IBM Notebooks, Pentium - 1/2/3/4/dual core/quad core..., SUN work stations, Origin 2000, PARAM 10000,IBM SP/2, Notebook, Ultrabook, Chromebook, Laptop etc.

Technology used:  KIPS(knowledge information processing system) and PROLOG(programming in logic language).


1. Generation number beyond  IV , have been used occasionally  to describe some current computer system that have a dominant organizational or application driven feature.
2. Computers based on artificial intelligence are available.
3. Computers use extensive parallel processing , multiple pipelines , multiple processors etc.
4. Massive parallel machines and extensively distributed system connected by communication networks fall in this category.
5. Introduced ULSI technology- Intel's Pentium 4 microprocessor contains 55 million transistors millions of components on a single IC  chip.
6. Superscalar processors , vector processors , SIMD processors , 32 bit micro controllers and embedded processors ,digital signal processors etc have been developed.
7. Memory chips  2 GB , hard disk drivers 360 GB  and optical disks 27 GB are available.
8. Object oriented language like JAVA  suitable for internet programming has been developed.
9. Portable note book computers introduced.
10. Storage technology advanced- large main memory and disk storage available.
11. Introduced world wide web.
12. New operating systems developed- Windows XP/7/8....,LINUX etc.
13. Got hot pluggable features- which enable a failed component to be replaced with a new one without the need to shutdown the system , allowing the up time of the system to be very high.
14. The recent development in the application of internet is the Grid technology which is still in its upcoming stage.
15. Quantum mechanism and nanotechnology will radically change the phase of computers.


1. Will work parallely.
2. Will have capability of performing multiple task at a time.
3. Will have capability of knowledge processing.
4. Will be a knowledge information processing system.
5. Will process basic intelligence.


1. Not yet known.


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