操作系统概念中文课后答案.pptx

操作系统概念中文课后答案PPT课件会计学1-cont.第1页/共34页2. What is the main advantage of multiprogramming?高效地使用CPU，通过重叠来自不同用户对CPU和I/O设备的需求增加CPU的利用，设法让CPU执行有意义的指令1-cont.第2页/共34页3. In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.a. What are two such problems?b. Can we ensure the same degree of security in a time-shared machine as we have in a dedicated machine? Explain your answer.用户之间互相偷数据、代码对系统资源使用的记账信息1-cont.第3页/共34页4. Define the essential properties of the following types of operating systems:a. Batch相似需求的Job分批、成组的在计算机上执行，Job由操作员或自动Job程序装置装载；可以通过采用 buffering, off-line operation, spooling, multiprogramming 等技术使CPU 和 I/O不停忙来提高性能批处理适合于需要极少用户交互的Job。b. Interactive由许多短交易组成，下一次交易的结果可能不可预知需要响应时间短1-cont.第4页/共34页c. Time sharing使用CPU调度和多道程序提供对系统的经济交互式使用，CPU快速地在用户之间切换一般从终端读取控制，输出立即打印到屏幕d. Real time在专门系统中使用，从传感器读取信息，必须在规定时间内作出响应以确保正确的执行1-cont.第5页/共34页e. Network在通用OS上添加联网、通信功能远程过程调用文件共享f. Distributed具有联网、通信功能提供远程过程调用提供多处理机的统一调度调度统一的存储管理分布式文件系统1-cont.第6页/共34页5. Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages and one disadvantage of multiprocessor systems?Symmetric multiprocessing中所有处理器同等对待，I/O可以在任意CPU上处理。Asymmetric multiprocessing具有一个主CPU和多个从CPU，主CPU将任务分派到从CPU，I/O通常只能由主CPU处理。多处理机系统的优点比多个计算机系统可能更省钱（同样CPU个数）执行程序更快可靠性更高缺点：软硬件更复杂6. thinking: what kind of features may exist in CC, IOT or CPS?Chapter 2第7页/共34页1. How does the distinction between monitor mode and user mode function as a rudimentary form of protection (security) system?通过建立一组只能在monitor mode才能执行的特权指令集，OS能够确保总是能控制整个系统。2-cont.第8页/共34页2. What are the differences between a trap and an interrupt? What is the use of each function?An interrupt是硬件产生的系统内的流的改变A trap是软件产生的“中断”。interrupt可以被I/O用来产生完成的信号，从而避免CPU对设备的轮询 A trap可以用来调用OS的例程或者捕获算术错误 2-cont.第9页/共34页3. Which of the following instructions should be privileged?a. Set value of timer.b. Read the clock.c. Clear memory.d. Turn off interrupts.e. Sw