There are five generations of computers defined based on the underlying hardware technology used. The first generation used vacuum tubes and were very large, expensive, and unreliable. The second generation introduced transistors, making computers smaller, more affordable, and reliable. The third generation used integrated circuits, further miniaturizing computers. The fourth generation saw the rise of microprocessors and personal computers. The fifth generation, starting in 1980, is based on ultra-large scale integration and artificial intelligence techniques.

1. COMPUTER - GENERATIONS
Computer Generations
Generation incomputer terminology is a change intechnology a computer is/was being used. Initially, the
generationtermwas used to distinguishbetweenvarying hardware technologies. But nowadays, generation
includes bothhardware and software, whichtogether make up anentire computer system.
There are totally five computer generations knowntilldate. Eachgenerationhas beendiscussedindetailalong
withtheir time period, characteristics. We've used approximate dates against eachgenerations whichare
normally accepted.
Following are the mainfive generations of computers
S.N. Generation & Description
1 First Generation
The period of first generation: 1946-1959. Vaccumtube based.
2 Second Generation
The period of second generation: 1959-1965. Transistor based.
3 Third Generation
The period of third generation: 1965-1971. Integrated Circuit based.
4 Fourth Generation
The period of fourthgeneration: 1971-1980. VLSI microprocessor based.
5 Fifth Generation
The period of fifthgeneration: 1980-onwards.ULSI microprocessor based
First Generation
The period of first generationwas 1946-1959.
First generationof computer started withusing vacuumtubes as the basic components for memory and circuitry
for CPU(CentralProcessing Unit). These tubes like electric bulbs produced a lot of heat and were prone to
frequent fusing of the installations, therefore, were very expensive and could be afforded only by very large
organisations.
Inthis generationmainly batchprocessing operating systemwere used. Inthis generationPunched cards,
Paper tape, Magnetic tape Input & Output device were used.
There were Machine code and electric wired board languages used.

2. The mainfeatures of First Generationare:
Vacuumtube technology
Unreliable
Supported Machine language only
Very costly
Generate lot of heat
Slow Input/Output device
Huge size
Need of A.C.
Nonportable
Consumed lot of electricity
Some computer of this generationwere:
ENIAC
EDVAC
UNIVAC
IBM-701
IBM-650
Second Generation
The period of second generationwas 1959-1965.
This generationusing the transistor were cheaper, consumed less power, more compact insize, more reliable
and faster thanthe first generationmachines made of vaccumtubes.Inthis generation, magnetic cores were

3. used as primary memory and magnetic tape and magnetic disks as secondary storage devices.
Inthis generationassembly language and highlevelprogramming language like FORTRAN, COBOL were
used.
There were Batchprocessing and Multiprogramming Operating systemused.
The mainfeatures of Second Generationare:
Use of transistors
Reliable as compared to First generationcomputers
Smaller size as compared to First generationcomputers
Generate less heat as compared to First generationcomputers
Consumed less electricity as compared to First generationcomputers
Faster thanfirst generationcomputers
Stillvery costly
A.C. needed
Support machine and assmebly languages
Some computer of this generationwere:
IBM 1620
IBM 7094
CDC 1604
CDC 3600
UNIVAC 1108
Third Generation
The period of third generationwas 1965-1971.
The third generationof computer is marked by the use of Integrated Circuits (IC's) inplace of transistors.A

4. single I.C has many transistors, resistors and capacitors along withthe associated circuitry.The I.C was invented
by Jack Kilby. This development made computers smaller insize, reliable and efficient.
Inthis generationRemote processing, Time-sharing, Real-time, Multi-programming Operating Systemwere
used.
Highlevellanguage (FORTRAN-II TO IV, COBOL, PASCAL PL/1, BASIC, ALGOL-68 etc.) were used during
this generation.
The mainfeatures of Third Generationare:
IC used
More reliable
Smaller size
Generate less heat
Faster
Lesser maintenance
Stillcostly
A.C needed
Consumed lesser electricity
Support highlevellanguage
Some computer of this generationwere:
IBM-360 series
Honeywell-6000 series
PDP(PersonalData Processor)
IBM-370/168
TDC-316
Fourth Generation
The period of FourthGenerationwas 1971-1980.

5. The fourthgenerationof computers is marked by the use of Very Large Scale Integrated (VLSI) circuits.VLSI
circuits having about 5000 transistors and other circuit elements and their associated circuits ona single chip
made it possible to have microcomputers of fourthgeneration. FourthGenerationcomputers became more
powerful, compact, reliable, and affordable. As a result, it gave rise to personalcomputer (PC) revolution.
Inthis generationTime sharing, Realtime, Networks, Distributed Operating Systemwere used.
Allthe Higher levellanguages like C and C++, DBASE etc. were used inthis generation.
The mainfeatures of FourthGenerationare:
VLSI technology used
Very cheap
Portable and reliable
Use of PC's
Very smallsize
Pipeline processing
No A.C. needed
Concept of internet was introduced
Great developments inthe fields of networks
Computers became easily available
Some computer of this generationwere:
DEC 10
STAR 1000
PDP 11

6. CRAY-1(Super Computer)
CRAY-X-MP(Super Computer)
Fifth Generation
The period of FifthGenerationis 1980-tilldate.
Inthe fifthgeneration, the VLSI technology became ULSI (Ultra Large Scale Integration) technology, resulting
inthe productionof microprocessor chips having tenmillionelectronic components.
This generationis based onparallelprocessing hardware and AI (ArtificialIntelligence) software.
AI is anemerging branchincomputer science, whichinterprets means and method of making computers think
like humanbeings.
Allthe Higher levellanguages like C and C++, Java, .Net etc. are used inthis generation.
AI includes:
Robotics
Neuralnetworks
Game Playing
Development of expert systems to make decisions inreallife situations.
Naturallanguage understanding and generation.
The mainfeatures of FifthGenerationare:
ULSI technology
Development of true artificialintelligence
Development of Naturallanguage processing
Advancement inParallelProcessing
Advancement inSuperconductor technology

7. More user friendly interfaces withmultimedia features
Availability of very powerfuland compact computers at cheaper rates
Some computer types of this generationare:
Desktop
Laptop
NoteBook
UltraBook
ChromeBook