The word computer comes from the word computes, which means to calculate. Hence a computer is normally a calculating device.The development phases of computer are known as computer generation. The generation of computer classified according to the technologies being applied to them.
Following are the main five generations of computers with explain :
The first large electronic computer device was completed by a team led by Eckert and Mauchly at the university of Pennsylvania in U.S.A in 1946. This computer was called Calculator and Electronic Numerical Integrator. This computer was made up using high speed vacuum tubes. It had a very small memorys.
First generation of computer were very expensive to operate and in addition to using a great deal of electricity, and generate a lot a of heat. And First generattion very expensive and could be afforded only by very large organisations.
First generation computer mainly batch processing operating system were used. In this generation of computer used Punched cards, Paper tape, Magnetic tape Input & Output device.
First generation of computers lowest-level programming language understood. used on machine language code, To perform operations, and they could only solve one problem at a time.
The major characterstics of first generation computer are as follows.
Second generation were developed During the period of 1956 to 1963. This generation in Transitor would replace the vacuum tubes. from the computer. The transistor was invented at Bell Telephone laboratories Bardeen, Brattain, and Shockley in 1947. Transistor soon proved to be a better electronic switching device then the vacuum tubes, due to their following properties.
This generation of computer are used the low low level language i.e. machine level language and assembly language. Second generation computer has faster input / output devices than their first generation computer. Second generation computer memory capacity was 4000 to 6000 characters. And Speed was up to one million instruction per second. Second generation are Faster and larger primary and secondary storage.
The first integrated circuit(Ic chip) invented by clair kilby and Robert Noyce in 1958.Integrated circuits are circuits consisting of several electronics components like transistor, and capacity grown on a single silicon chip. These chips are very small in size and eliminated wired interconnection between components. Initially the IC chips contained only ten to twenty componenets. This technology was called Small Scale Integration (SSI). Later about hundred components would be integrated on a single chip. This technology was named Medium Scale Integration(MSI)
IC chips are much smaller, less expansive to produce, More reliable, Fast in operation, Dissipated less heat and consumed less power than circuits build by wiring electronic components manually. Hence the third generation of computer were more powerful, more reliable,less expensive,smaller, and cooler to operate than the second generation computers. Third generation of computer remote processing,multiprogramming operating system,time-sharing were used. High-level languages uses in this generation of computer eg.FORTRAN-II TO IV, COBOL, PASCAL PL/1, BASIC, ALGOL-68 etc.
The characteristics of third Generation computer :
Fourth generation of computer invented was 1971 - 1980.IC chips was introduced in third generation, later the Large Scale Integration (LSI) was possible in which over 30000 electronics was integrated,Followed by VLSI (very Large Scale Integration) When it was possible to integrate about one million electronic components on a single chip. This process led to a microprocessor. A microprocessor contains all the circuits needed to perform arithmetic logic unit and control unitfunctions, the core activities of all computers on a single chip. Hence it became possible to built a complete computer using microprocessor. It started a new revolution of computer known as Personal Computer(PC) PC's are very compact in size and inexpensive so it became for any one to own a computer.
In this generation magnetic core memories were replaced by semiconductor memories, It became large random access memories with fast access time. Hard disk became smaller, cheaper, and larger in capacity. Magnetic tapes, Floppy disks became very popular as a portable storage media.
Characterstics of Fourth Generation of Computers :
In this generation we need most powerful computer. The Ultra Large Scale Integration (ULSI) technology is used to product processor chips, having ten milion electronic components. The size of main memory is larger than 1 GB and capacity of hard disk doubled almost in every year. 180 GB HDD capacity is very common for this generation of computer. In this generation very powerful and compact computers becoming available at very low rates. In this generation portable notebook computers are available, which gives the power of PC to their users even while traveling. A powerful desktop PC's and workstation, powerful servers and very powerful supercomputers are available.
Storage technology is very advance and fast in this generation. Optical disk and blue ray disks cow store 750MB to 40GB. In this Generation Communication technology become faster day by day. The internet made if possible for computer users sitting across the globe to communicate with each other within minutes by using email facility.
In this generation use high-level language like C and C++ , Java, .Net etc.