●真正安全的密码系统应是 (64) 。

● (65) 标准是国际标准化组织中质量管理和质量保证技术委员会制定的所有标准。

●A local area network(LAN)is the communication of a number of computers by (66) connecting to each one in a single location,usually a single floor of a building or all the computers in a small company.

●The standard (67) in C language contain many useful functions for input and output，string handling，mathematical computations，and system programming tasks.

●The OSI (68) model，sometimes also called ISO or 7 layers reference model for communication.has been developed by the International Standards Organization in early 1980's.

●If your diskette has been (69) ，the computer can not store any new information on it.