Here size of computers means categorization of computers as per their processing speed, memory capacity and number of users a computer can handle simultaneously.
Large size computers, normally, can handle large number of users and large number of powerful input and output devices.
Whereas small size computers, normally, are used by one user at a time, and can handle fewer input and output devices.
On the basis of sizes, computers can be divided into following categories:
§ Micro Computers
§ Mini Computers
§ Main Frames
§ Super Computer
§ Work Stations
§ Micro Computer is the smallest size computer system.
§ These computers are known as single user computers that one user can use this type of computer at a time.
§ Micro Computer is primarily based on chip known as Microprocessor, e.g. Core2 Duo, Pentium – III, etc. Micro Computer is low cost and user – friendly computer.
§ Micro Computer uses variety of user friendly software, such as Window, which helps to provide user- friendly operation of microcomputers.
§ These computers are the most popular type of computers.
§ Micro Computers are general purpose computers that these computers can be used for any type of applications like accounting, designing and gaming applications, etc.
§ Micro Computer is also known as Personal Computer.
§ Major Suppliers of Micro Computers are Dell, HP, Compaq, Apple Computer etc.
§ Between Micro Computer and Mini Computer there is another class of computer in terms of processing power, these computers are known asWork Stations.
§ A Work Station is just like a microcomputer and at a time it is also used by one person / user only.
§ Normally, a Work Station term is used when a micro computer is connected to a powerful server in networking mode.
§ But there are standalone workstations, which normally work on UNIX operating system and uses RISC (Reduced Instructions Set Computing) architecture of CPU for fast processing of instructions.
§ These computers are known as multi-users computer that many persons / users can be connected to same CPU.
§ Mini Computers are larger in size, more powerful and expensive computers than microcomputers.
§ There is no clear distinction between minicomputer and mainframe; it is normally a difference of numbers of users and memory capacity, etc.
§ Mini Computers are normally based on UNIX operating system and used by big organization like Banks, Railway etc. unlike micro computers which can execute many different applications together.
§ Major Suppliers of Mini Computer are IBM, Sun Micro Systems and DELL.
§ Mainframes are larger and costlier computers than minicomputers.
§ Mainframes offer faster processing speed and greater storage space than a minicomputer.
§ Also, Mainframe can support much larger number of users uses the same system together.
§ Mainframe Computer is normally used as Central Computer of big organization like Stock Exchange, Banks Head Office etc.
§ Mainframe systems are very costly systems.
§ The IBM is the most popular supplier of mainframe computer.
§ These are the largest, fastest and most expensive computer systems.
§ These systems are very expensive and normally not used for commercial data processing.
§ These computers, primarily, are designed to process complex scientific applications such as weather forecasting and missile development etc.
§ Super Computer mainly does the parallel processing that is one supercomputer employ so many processor, which works in parallel to perform large numbers of complex operation simultaneously.
§ Super Computer can support 10s of thousand users simultaneously.
§ Super Computer instruction processing speed is measured in BIPS (Billion of Instructions per Second).
§ Major Suppliers of Super Computer are CRAY, IBM, and Sun Microsystems.
§ A Server is a computer system which is used in networks like LAN and WAN, etc.
§ A Server is used to provide services to many other computers, normally known as clients of that server.
§ For Example: When we are connected to Yahoo’s web server then our computer acts as client of Yahoo’s server.
§ A server is not only a computer hardware, rather it is a combination of hardware and software; which helps to provide the required services to many computers / users connected with server, simultaneously.
§ Any computer can act as server depending upon its configuration.
§ However, there are special server computer also in the market, which are provided by computer manufactures to provide optimized network services.
§ A server uses some hardware and software to provide shareable services.
§ Some common examples of servers are Web Server, Print Server, File Server, and E-mail Server, e