西电软院OS复习整理.pdf

OS 管锥九篇 昔者有云：以管窥天，所窥者大，所见者小；以锥插地，所刺者巨，所中者小。 OS 乃恩师航博士亲自授传。临至期末，始觉有kd 之嫌，众人之惑正亦。 不求高分但求保过，亲自总结此文，名曰管锥九篇。寓意乃 OS 本博大精深，此文不过管锥 之见，应对考试而已。 但愿有缘人从中拾得一点收获，己莫大满足矣。 癸巳年岁末于西电 李欢 一 简介 1. For this reason,computers are equipped with a layer of software called the operating system, whose job is to provide user programs with a better, simpler, cleaner, model of the computer and to handle managing all the resources just mentioned. 2. The program that users interact with, usually called the shell when it is text based and the GUI (Graphical User Interface). 3. Most computers have two modes of operation:kernel mode and user mode.The operating system is the most fundamental piece of soft-ware and runs in kernel mode(also called supervisor mode).In this mode it has complete access to all the hardware and can execute any instruction the machine is capable of executing.The rest of the software runs in user mode,in which only a subset of the machine instructions is available. 内核态中，OS 拥有对所有的硬件的完全访问权，可以执行及其能够运行的任何指令。软件的 其余部分运行在用户态下，只使用了机器指令中的一个子集。 4. To obtain services from the operating system, a user program must make a system call, which traps into the kernel and invokes the operating system. 二 进程和线程 Processes 1. 进程拥有各自独立的地址空间，进程共用一段地址空间。 2. In this model, all the runnable software on the computer, sometimes including the operating system, is organized into a number of sequential processes, or just processes for short. A process is just an instance of an executing program, in-cluding the current values of the program counter, registers, and variables. Con-ceptually, each process has its own virtual CPU. In reality, of course, the real CPU switches back and forth from process to process. 3. This rapid switching back and forth is called multiprogramming. Some-times people speak of pseudoparalleli