computer

computer is a machine that manipulates data and stores it with the set of instructions given to it.

Classifications:
The first four generations of computers were based on the techonology of the age to which they belonged. They were thus based on the vacuum tube technology; the transister and printed circuit technoloty; the integrated circuit technoloty and very large scale integrated ( VLSI) technoloty, respectively. The marvel of the fourth generation VLSI technology is that a micro chip weighing a few grams-a thin silicon chip using 0.13 micron techonology [SDRAM] has a memory capability of 1 GB[100 crores of bits of 0s and 1s equivalent of 8000 news paper pages] presently the development has entered areas of "Artificial Intelligence". There are generally called fifth generation computers.
Today computers can be classified as mainframe computers, mini computers and micro-computers

MAIN FRAME COMPUTERS:
These are expensive,large, centralised computer facilities where a super computer is connected to several terminals. A multi user main frame computer has a large memory and is capable of speeds of the order of several billions of floating-point oprations per second (Flops).

MINI COMPUTERS:
These are also multiuser computers comparitively operating at slower speeds and lesser memory. In the mini computer category are the extremely popular DEC10,PDP-11 and VAX-11 computers of the digital equipment corporation (DEC)

MICRO COMPUTERS:
These are based on stndard micro processors marketed by intel,motorola etc..,.A Micro Processor is a single silicon electronic chip which contains the ALU and the control unit.
Micro Computers are often called as personal computers or PCs.Since they were originally intended to be single either at office or home.The home computers is a PC providing education,entertainment,information and communication facilities at home.Now-a-days one can send e-mails,e-greetings,chat,play games,hear music,watch video,video conferencing,banking operations,reserve travel tickets with help of home PC and internet without leaving ones home