虚拟存储管理系统的基础是程序的(7)理论，这个理论的基本含义是指程序执行时往往会不均匀地访问主存储器单元。根据这个理论，Denning提出了工作集理论。工作集是进程运行时被频繁地访问的页面集合。在进程运行时，如果它的工作集页面都在(8)内，能够使该进程有效地运行，否则会出现频繁的页面调入/调出现象。

(81)

(79)

(80)

Flow control is a function that prevents network congestion by ensuring that(71)do not overwhelm(72)with data. There are three commonly used methods for handling network congestion.(73)is used by network devices to temporarily store bursts of excess data in memory until they can be processed. (74)are used by receiving devices to help prevent their buffers from overflowing.(75)is a flow -control scheme in which the source device requires an acknowledgment from the destination after a certain number of packets have been transmitted.

(78)

(76)

(75)

(73)

(74)

The purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable (66) of the technical requirements for the software product.

 During the requirements definition phase, the requirements definition team uses an iterative process to expand a broad statement of the system requirements into a complete and detailed specification of each function that the software must perform. and each (67) that it must meet. The starting point is usually a set of high-level requirements from the (68) that describe the project or problem.

 In either case, the requirements definition team formulates an overall concept for the system and the defines (69) showing how the system will be operated, publishes the system and operation concept documents,and conducts a system concept review(SCR).

 Following the SCR, the team derives (70) requirements for the system from the highlevel requirements and the system operations concept. Using structured or object-oriented analysis, the team specifies the software functions and algorithms needed to satisfy each detailed requirements.