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处理机管理功能 进程控制    在传统的多道程序环境下,要使作业运行,必须先为它创建一个或几个进程,并为之分配必要的资源。当进程运行结束时,立即撤消该进程,以便能及时回收该进程所占用的各类资源。进程控制的 ...
As I sat perched in the second-floor window of our brick schoolhouse that afternoon, my heart began to sink further with each passing car. This was a day I'd looked forward to for weeks: Miss Pace's fourth-grade, end-of-the-year party.Miss Pace had kept a running countdown on the blackboard all that ...
Have you ever known a married couple that just didn't seem as though they should fit together -- yet they are both happy in the marriage, and you can't figure out why? I know of one couple: He is a burly ex-athlete who, in addition to being a successful salesman, coaches Little League, is active in ...
并发性(Concurrence)    并行性和并发性是既相似又有区别的两个概念,并行性是指两个或多个事件在同一时刻发生;而并发性是指两个或多个事件在同一时间间隔内发生。在多道程序环境下,并发性是指在一段时间内,宏观上有多个程序在同时运行,但在单处理机系统中,每一时刻却仅能有一道程序执行,故微观上这些程序只能是分时地交替执行。倘若在计算机系统中有多个处理机,则这些可以并发执行的程序便可被分配到多个处理机上,实现并行执行,即利用每个处理机来处理一个可并发执行的程序,这样,多个程序便可同时执行。 共享(Sharing)    在操作系统环境下,所谓共享是指系统中的资源可供内存中多个并发执行的进 ...
分时系统(Time-Shaing System)    如果说,推动多道批处理系统形成和发展的主要动力,是提高资源利用率和系统吞吐量,那么,推动分时系统形成和发展的主要动力,则是用户的需求。或者说,分时系统是为了满足用户需求所形成的一种新型OS。它与多道批处理系统之间,有着截然不同的性能差别。用户的需求具体表现在以下几个方面: 引用   1.人-机交互   2.共享主机   3.便于用户上机 分时系统实现中的关键问题   为实现分时系统,其中,最关键的问题是如何使用户与自己的作业进行交互,即当用户在自己的终端上键入命令时,系统应能及时接收并及时处理该命令,再将结果返回给用户。此后,用户可继续 ...
  The effort to save the environment derives much of its political popularity from the impact of immediate personal inconveniences:a sewage polluted beach the smong that leaves one's eyes watering, the black granules of soot that drift in through an open window, traffic jams,noise, the smoking vehicl ...
Joshua Loth Liebman "On my head pour only the sweet waters of serenity. Give me the gift of the Untroubled Mind." Once, as a yongy man full of exuberant fancy, I undertollk to draw up a catalogue of the acknowledged "goods"of life. As other men sometimes tabulate lists of proper ...
操作系统的目标    目前存在着多种类型的OS,不同类型的OS,其目标各有所侧重。通常在计算机硬件上配置的OS,其目标有以下几点: 引用 1.方便性 2.有效性 3.可扩充性 4.开放性 操作系统的作用 1.OS作为用户与计算机硬件系统之间的接口。    OS处于用户与计算机硬件系统之间,用户通过OS来使用计算机系统。或者说,用户在OS帮助下,能够方便、快捷、安全、可靠地操纵计算机硬件和运行自己的程序。 注意:OS是一个系统软件,因而这种接口是软件接口。 OS作为接口的图,请参考附件。 引用 1.命令方式。这是指由OS提供了一组联机命令(语言),用户可通过键盘输入有关命令,来直接操作计算 ...
A person is a book. Reading a person is more difficult than reading a book written in other languages. I read the Book of Person seriously to such an extent than I can't understand it event though I have lived through more half of my life. On a sunny and clear day, somebody is willing to lend his u ...
java SE应用程序共同的问题 在java SE应用程序中的问题与资源有关的有:内存、线程、类和锁。资源冲突或泄漏可能导致性能问题或意想不到的错误。 问题症状诊断工具 内存不足 OutOfMemoryErrorjava堆分析工具(jhat) 内存泄漏 1.内存的 ...
Fear od something bad happening in the future is one of the things that make us human.   Animal might fear an immediate danger,that is happening right now,but only we fear something that might happen, that isn't happening now, that isn't even showing its ugly face at the moment. This fear,some mig ...
Chemistry on an experiment called the crystal. First the formation of chemical substances dissolved in water solution, solution Sheng Yu evaporating dish, the eavporating dish placed in steel tripod, the following alcohol lamp heating, control-related conditions, can be a different crystals.Crystal i ...
软件开发时一套关于软件开发各阶段的定义,任务、作用的,建立在理论上的一门工程学科。它对解决软件危机,指导人们利用科学、有效的方法来开发软件,提高及保证软件开发的效率和质量起到了一定的作用。 经典的软件工程思想将软件开发分成以下5个阶段: 引用   需求分析(Requirements Capture)阶段   系统分析与设计(System Analysis and Design)阶段   系统实现(Implementation)阶段   测试阶段(Testing)   维护阶段(Maintenance) UML的内容: UML的定义包括UML语义和UML表示法两个部分。 UML可 ...
  Thank you. I'm honored to be with you today for your commencement from one of the finest universities in the world. Truth be told, I never graduated from college and this is the cloesest I've ever gotten to a college graduation.   Today I want to tell you three stories from my life. That's it. No ...
精简指令集计算机    精简指令集计算机RISC(Reduced Instruction Set Computer).RISC结构是相对于传统的采用微程序结构的复杂指令集计算机CISC(Complex Instruction Set Computer)结构而言的。它的出现时计算机体系结构发展使上一个重要的里程碑 ...
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