Computer is perhaps the most powerful and versatile tool ever created by man. "generation" in computer provides a framework for the growth of the computer industry . there are totally five computer generation known untill dotay . each generation has been discussed below in detail along with its identifying characteristics . ~~>>  First Generation (1942 - 1955)   The first business computer was developed in the year 1951 by U.S. census bureau. This computer was called un :ivarsal automatic computer (UNIVAC) . The technology was based on vacuum tubes . The vacuum tube circuits contained a filament that was heated to emit electrons . Main Features : 1>>  Bulky in size , requiring large rooms for installation. 2>>  Very expensive . 3>>  As large number of vecuum tubes were used that emitted large amount of heat , so result of that air condioned was used . 4>> processor speed measured in milliseconds . 5>>  power consumption of these computer was very high .   ~~>> Second Generation (1955 - 1964) The computer that used transistor were called the second genration computer i.e. in this era transistors were used in place of vacume tubes . Transistors are electronic circuitc that are small in size and do not require any heating for emitting electrons . Main Features : 1>> They consuined less power than the first - generation computer . 2>>  Heat dissipation was much less then first - generation computer . 3>> Speed was ten time faster than first generation computer . 4>>  Large primary and secondary storage as compared to firat -  generation computer . 5>> More reliable and less prone to errors .   ~~>> Third Generation (1964 - 1974)   In this generation " Large Scale Integration " (LSI) circuits were used . The LSI circuits were invented in mid - 1960s. LSI circuits integrate several circuit components into a single chip . Main Features : 1>>  Smaller in size 2>>  Portable 3>>  The use of high lenguage were possible. 4>>  Less power consumed than the second generation computer . 5>>  Processor speed measured in nanoseconds . 6>>  Improvement in cost performance factor .   ~~>> Fourth Generation (1974 - 1988)   Very Large Scale Integrated (VLSI) chips were invented in the year 1969 .The computers that used VLSI  are called the fourth generation computer . During the fourth generation , magnetic core memories were replaced by semiconductor memories . The introduction of standard arthitecture helped in greater mobility of system , the introduction of micro - technology and significant software developments . Main Features : 1>> Very small in size 2>>  Very reliable and cheaper 3>>  They were totally general purpose computer . 4>>  Graphical User Interface ( GUI ) enabled new user to quickly learn how to use computers . 5>>  Sharing of computer resource like disks , printer etc . can possible among multiple computer and thair use .   ~~>> Fifth Generation (1988 - present)   Recent research has focused on developing ' thinking computer ' i.e. artificial intelligency in computers . Currently scientist are trying to develope a computer that can think like a human act like a human . These computer are called fifth generation computers and are developed in the laboratories of U.S.A. and Japan. These computer will have K.I.P.S. ( Knowledge Information Processing syster ) . In reality we have entered in the era of generationless computer because no single innovation is or will be , good enough to name another generation of computer