Title Unit I.pdf ✅

3 Generation Period Description First 1940-1955 Vacuum tube based. Second 1955-1964 Transistor based. Third 1964-1975 Integrated Circuit based. Fourth 1975-1989 VLSI microprocessor based. Fifth 1989-onwards ULSI microprocessor based. 1) First Generation Of Computer (1940–1955): The digital computers using electronic vaccume tubes are known as First Generation of Computers. A Vaccume tube was a delicate glass tube which used filament as a source of electron and could control and amplify electronic signals. It was only high speed electronic switching device available in those days and it perform operations in milliseconds. The memory of these computers used was electromagnetic relay and all data and instructions were written in machine and low level assembly language. Since these language was very difficult to work so only few specialists understood how to program these computers. Characteristic features are as follows. They were too bulky in size so requiring rooms for installation. 1) Thousands of Vaccume tubes were used and they emitted large amount of heat and burnt out frequently. Hence rooms or areas where computers were located had to be properly air conditioned. 2) A Vaccume tube filament had limited life and as computer used thousands of vaccume tubes so it leads to frequent hardware failure so need constant maintenance. 3) As each Vaccume tube consumed about half watt of power and computer which consist of thousand of Vaccume tubes, power consumption was very high. 4) As thousand of components assembled manually by hand into electronic circuit, hence commercial production of these computers was difficult and costly. 5) As programming of these computers was very difficult so it lead to limited commercial use. Examples: IBM 701, ENIAC (Electronic Numerical Integrator and Computer), EDVAC (Electronic Discrete Variable Automatic Computer), UNIVAC (Universal Automatic Computer). Vaccume Tube IBM 701 ENIAC ENIAC IBM 70 EDVAC UNIVAC UNIVAC 2) Second Generation Of Computer (1955–1964): The digital computers using transistors instead of Vaccume tube are known as Second Generation of Computers. These transistors were a highly reliable, more rugged, easier to handle, operate almost 10 times faster than Vaccume tube, consumed almost one tenth power than power consumed by Vaccume tube, smaller in size, less
4 expensive, dissipated less heat. So due to these properties of transistors, computers in 2nd generation were more powerful, more reliable, less expensive, smaller and cooler to operate as compared to 1st generation of computer. They used magnetic cores for main memory, magnetic disk and tape as secondary storage and punched cards used for feeding programs and data to these computers. High level languages like FORTRAN, COBOL, ALGOL and SNOBOL and batch operating system emerged during 2nd generation. This language is much easier as compared to 1st generation. Multiple batch operating systems enable multiple jobs batched together and submitted at a time. This results in faster processing, easier operation as compared to 1st generation computers. 1st generation computers were mainly used for scientific calculations, while 2nd generation computers were highly used in business and industry for commercial data processing applications like Payroll, inventory control, marketing and production planning. Characteristic features are as follows. 1) They were more than 10 times faster than 1st generation computer. 2) They were smaller and required smaller space as compared to 1st generation computer. 3) They were consume less power and less heat dissipated than 1st generation computers, still required proper air conditioned. 4) They were more reliable so less hardware failure than 1st generation computer. 5) They had faster and larger primary and secondary storage as compared to 1st generation computer. 6) In these computers, as thousand of transistors assembled manually by hand into electronic circuit, hence commercial production of these computers was difficult and costly. 7) They were easier to program than 1st generation computer, so it they had wider commercial use. Examples: IBM 1620, IBM 7090, IBM 7094I, IBM 7094II, CDC 1604 (CDC -Control data corporation), PDP1, (PDP – Programmed Data Processor), PDP5, PDP 8 Transistor IBM 1620 IBM 7090 CDC 1604 IBM 7090 CDC PDP 1 PDP 1 3) Third Generation Of Computer (1964–1975): The digital computers where several electronic components like transistors, resistors and capacitors were replaced by Integrated Circuit (IC) or chip are known as Third Generation of Computers. It initially use SSI (Small Scale Integration) where 10-20 components mounted on single IC. Later MSI (Medium Scale Integration) where hundred components were mounted on single chip was developed. IC’s where smaller and circuit assembled by wiring electronic components manually. Hence these computers in 3rd generation were more powerful, more reliable, less expensive, smaller and cooler to operate as compared to 2nd generation of computer. They used magnetic cores for main memory, magnetic disk and tape as secondary storage and punched cards used for feeding programs and data to these computers. High level languages like FORTRAN, COBOL was most powerful in those days. ANSI (American National Standard Institute) standardized them in 1966 and 1968 respectively and standardized versions were called ANSI FORTRAN and ANSI COBOL respectively. Also PL/1, PASCAL, BASIC language used in 3rd generation computers. Characteristic features are as follows. 1) They were more powerful and capable of performing about 1 million instructions per second. 2) They were smaller and required smaller space as compared to 2nd generation computer. 3) They were consume less power and less heat dissipated than 2nd generation computers, still required proper air conditioned.