A microcomputer is a desktop or notebook size computing device that uses a microprocessor as its Central Processing Unit， or CPU. Microcomputers are also called Personal Computers （PCs）， home computers， small business computers， and micros. The smallest， most compact are called laptops. When they first appeared， they were considered single user devices， and they were capable of handling only four， eight， or 16 bits of information at one time. More recently the distinction between microcomputers and large， mainframe computers （as well as the smaller mainframe type systems called minicomputers） has become blurred， as newer microcomputer models have increased the speed and data handling capabilities of their CPUs into the 256 bit， or even much more bit multi-user range.
Microcomputers are designed for use in homes， schools， and office settings. Within the home， they can serve both as a tool for home management （balancing the family checkbook， structuring the family budget， indexing recipes） and as a recreational device （playing computer games， cataloging records and books）. Schoolchildren can use microcomputers for doing their homework， and in fact many public schools now employ the devices for programmed learning and computer literacy courses. Small business may purchase microcomputers for word processing， bookkeeping， the storage and handling of mailing lists and so on.
2．Minicomputer
A minicomputer is a mid-level computer built to perform complex computations while dealing efficiently with a high level of input and output from users connected via terminals. Minicomputers also frequently connect to other minicomputers on a network and distribute processing among all the attached machines. Minicomputers are used heavily in transaction processing applications and as interfaces between mainframe computer systems and wide area networks.
3．Mainframe Computer
A mainframe computer is a high level computer designed for the most intensive computational tasks. Mainframe computers are often shared by multiple users connected to the computer via terminals. The most powerful mainframes， called supercomputers， perform highly complex and time consuming computations and are used heavily in both pure and applied research by scientists， large businesses， and the military.
4．Supercomputer
In computer science， supercomputers are large， extremely fast， and expensive computers used for complex or sophisticated calculations， typically， machines capable of pipelining instruction execution and providing vector instructions. A supercomputer can， for example， perform the enormous number of calculations required to draw and animate a moving spaceship in a motion picture. Supercomputers are also used for weather forecasting， large scale scientific modeling， and oil exploration and so on and so like.
【New Words】
minicomputer 小型机
recreational 修养的，娱乐的
sophisticate 诡辩的，久经世故的人 calculation 计算，考虑
1.2 Computer in Action
Today we are witnessing one of the most dramatic technologies ever developed-the computer.
Computers are used in large and small business， government， education， health care， and almost all other profession.
Computers are used in almost every field of business. In investment， computers are used to get-up–to–the minute information on stocks and bonds and to make split-second buy and sell decisions. In real estate and finance， computers are used to investigate cash flow， return on investment， and depreciation. Banks use computer to process the huge amount of checks and credit card transactions that take place daily. Without computers， today’s banks couldn’t handle the large number of transactions that take place every second. In manufacturing， computers are used to design new products， control manufacturing equipment， and regulate inventory and other raw materials. Computers are used to automatically place orders， alert customers when there are possible stock outs， and help managers control every aspect of a manufacturing operation. Computerized robots are used to paint， weld， fasten， and attach parts along the assembly line. Computers are also used at the retail and wholesale level. At the retail level， computers are used to check out customers quickly at grocery stores， hardware stores， and department stores. They are also used to determine where to locate retail and wholesale facilities. The best shipping pattern between factories， warehouse， wholesale outlets， and retail establishments can also be determined quickly and efficiently.
The computer has had a profound effect on office procedures. With word processing， companies can electronically store key paragraphs. Then these key paragraphs can be called up on a screen， rearranged in every conceivable manner， and printed. Some word processing programs have dictionaries with over 100，000words， which automatically check spelling and grammar. Electronic mail （E-mail） is another exciting innovation in office automation. Acting like mailboxes and postal service， the computer quickly and efficiently routs messages to the appropriate individuals. With voice storage and forwarding， people can use the telephone to dial up a computer to leave instructions or messages for other people. Once stored， these verbal messages can be transcribed and printed electronically， they can be stored for future reference and action， and they can be forwarded using electronic mail to locations throughout the world. Think of a facsimile machine as a copy machine where the original document is placed in the FAX machine at one location and a copy of the original document appears on another FAX machine at another location.