section 5-5 电气工程及其自动化专业英语课件.pptVIP

* Chapter 5 Computer Section 5 Computer Network Basics Text New Words and Expressions Exercises End Translation of Sentences with Passive voice Section 5 Computer Network Basics There are reasons why people wish to connect computers together. Some of the most important reasons are: （1）Users working at their own computers, often in different locations, have access to programs, files, data from a data base, documents, and the like that are stored elsewhere. The users can also communicate using e-mail or talk services, or they can use groupware to work together on documents. Section 5 Computer Network Basics （2）It is often desirable to share valuable resources such as printers, a large disk facility, programs, or a data base among two or more computers. （3）Users may connect their computers to powerful computer resources to obtain support services, conduct business, purchase goods, discuss common interests, play games, or simply socialize. Section 5 Computer Network Basics （4）Computers can be used together to increase system reliability by providing redundant processing. Two or more CPUs can be executing the same program, and the results can be compared by the computers continuously. Connecting computers together also makes it possible to switch processing to a backup computer in the event of failure of a CPU. Such systems are called fault-tolerant systems. Fault-tolerant systems often provide redundancy on other devices, such as disks, as well. Disk arrays are well suited for fault tolerant computing. Section 5 Computer Network Basics （5）Computer power can be increased by combining multiple CPUs or computers work together. Grouping multiple CPUs means that multiple processes can be executed simultaneously. As another approach, a program may be executed more rapidly by distributing its execution so that each connected CPU or computer may be executing different parts of the program. Section 5 Computer Network Basics Actually, it is rare tod