OS复习笔记by李嘉良.docx

操作系统复习笔记 李嘉良共17页 9K多字，大家复习愉快第一章1.操作系统的目录Operating systemControls and coordinates use of hardware among various applications and usersStructure硬件，操作系统，应用软件，用户OperationComputer-System Operation?计算机系统运行*I/O 设备与 CPU 可并行运行I/O devices and the CPU can execute concurrently*每一设备控制器负责一个设备类型Each device controller is in charge of a particular device type*每一设备控制器有一局部缓存Each device controller has a local buffer*CPU 通过局部缓存与主存交换数据CPU moves data from/to main memory to/from local buffers*I/O 从设备到设备控制器的局部缓存I/O is from the device to local buffer of controller*设备控制器通过引起?中断?通知 CPU 操作已完成Device controller informs CPU that it has finished its operation by causing an?interruptStartupCommon Functions of Interrupts?中断的常见功能*通常中断通过?中断矢量?把控制传送给中断服务程序，该中断矢量包含了所有服务程序的地址?Interrupts transfers control to the interrupt service routine generally, through the?interrupt vector?, which contains the addresses of all the service routines*中断体系结构必须保护被中断指令的地址?Interrupt architecture must save the address of the interrupted instruction*当另一个中断正在处理时，刚进入的中断不能作用，以免?丢失中断?Incoming interrupts are?disabled?while another interrupt is being processed to prevent a?lost interrupt*陷阱是由于出错或用户请求引起的软件生成的中断?A?trap?is a software-generated interrupt caused either by an error or a user request*操作系统是中断驱动的?An operating system is?interrupt?drivenInterrupt Handling?中断处理*操作系统通过存储寄存器和程序计数器而保留了 CPU 的状态?The operating system preserves the state of the CPU by storing registers and the program counter*确定哪一种中断发生了?Determines which type of interrupt has occurred:*-轮询?polling*-矢量化中断系统?vectored interrupt system*对每一类中断分离代码段，以确定应该采取什么反应?Separate segments of code determine what action should be taken for each type of interrupt2.*中断的概念中断：指当出现需要时，CPU暂时停止当前程序的执行转而执行处理新情况的程序和执行过程。为什么需要中断？处理器的速度跟外围硬件设备的速度往往不在一个数量级上，因此，如果内核采取让处理器向硬件发出一个请求，然后专门等待回应的办法，显然降低内核效率。现代操作系统是由中断驱动（interrupt driven）的，中断分为硬件中断和软件中断。Event 是由interrupt（硬件中断）或者trap/exception（软件中断：陷阱/异常）引起，发生时，处理器捕捉到一个执行线程，并且将控制权转移到操作系统中某一个固定地址的机制。如果计算机没有进程要执行，没有用户响应请求，操作系统将等待某个事件的发生。而事件总是由中断或者陷阱引起的。起因：用户请求