Chapter 2:操作系统的组织结构H U S T K e S h i内容n操作系统虚拟机n操作系统的组织结构n硬件支持l处理机的态l中断DefinitionAn Operating System (OS) provides a virtual machine on top of the real hardware, whose interface is more convenient than the raw hardware interface.Hardware ApplicationsOperating SystemOS interfacePhysical machine interface AdvantagesEasy to use, simpler to code, more reliable, more secure, …You can say: “I want to write XYZ into file ABC ”n A operating system virtual machine takes the layeredapproach to its logical conclusion. It treats hardware and theoperating system kernel as though they were all hardware 命令解释、图形用户界面、用户程序系统调用文件系统处理机调度、内存管理设备驱动，中断处理裸机ØA virtual machine provides an interface identical to theunderlying bare hardwareØThe operating systemcreates the illusion of multipleprocesses, each executing onits own processor with its own(virtual) memory操作系统中的虚拟化技术n The resources of the physical computer are shared to create the virtual resourcesl处理器虚拟化-CPU scheduling can create theappearance that users have their own processor l主存的虚拟化-Virtual memory can create theappearance that processes have their own memoryspacel设备的虚拟化-Spooling and a file system can provide virtual card readers and virtual line printersl A normal user time-sharing terminal serves as the virtual machine operator’s console虚拟化技术及虚拟机软件(a) Nonvirtual machine (b) virtual machineØVirtualbox 、VMWare 、Xen ＋＋等流行的虚拟机软件提供基础计算设施的虚拟化服务ØAlan Turing showedthat any computer systemwith sufficient power can“emulate ” any otherØOne computer can“emulate ” anothercomputerVMWare Structure虚拟化技术及虚拟机软件n隔离和保护The virtual-machine concept provides complete protection of system resources since each virtual machine isisolated from all other virtual machines. This isolation, however, permits no direct sharing of resources.n方便操作系统研究与开发A virtual-machine system is a perfect vehicle for operating-systems research and development. System development is done on the virtual machine, instead of on aphysical machine and so does not disrupt normal system operation. n The virtual machine concept is difficult to implement due to the effort required to provide an exact duplicate to the underlyingmachine应用程序-----------------------虚机器界面操作系统-----------------------物理机器界面硬件假如没有操作系统？怎样将目标代码送给硬件？怎样输出打印结果？→人们将对二进制程序操作从二极发光管读答案操作系统的接口操作系统的组织结构n结构随着操作系统的发展，功能越强，OS自身代码量越大－采用良好的结构：有利于保证正确性以及自身修改和扩充。
