計算機系統(tǒng)結(jié)構(gòu)2英

Chapter 3 Operating-System Structuresn System Componentsn Operating System Servicesn System Callsn System Programsn System Structure n Virtual Machinesn System Design and Implementation Chapter 3 Operating-System Structuresn System Componentsn Operating System Servicesn System Callsn System Programsn System Structure n Virtual Machinesn System Design and Implementation Common System Componentsn Process Managementn Main Memory Managementn Secondary-Storage Managementn I/O System Managementn File Managementn Protection System n Networkingn Command-Interpreter System Process Managementn A process is a program in execution. A process needs certain resources, including CPU time, memory, files, and I/O devices, to accomplish its task.n The operating system is responsible for the following activities in connection with process management. 在同進程管理有關(guān)的活動中，操作系統(tǒng)負(fù)責(zé)下列事務(wù) n Process creation and deletion. n process suspension and resumption. n Provision of mechanisms for n process synchronizationn process communication Main-Memory Managementn Memory is a large array of words or bytes, each with its own address. It is a repository of quickly accessible data shared by the CPU and I/O devices.n Main memory is a volatile storage device. It loses its contents in the case of system failure.n The operating system is responsible for the following activities in connections with memory management: n Keep track of which parts of memory are currently being used and by whom.n Decide which processes to load when memory space becomes available.n Allocate and deallocate memory space as needed. Secondary-Storage Managementn Since main memory (primary storage) is volatile and too small to accommodate all data and programs permanently, the computer system must provide secondary storage to back up main memory. n Most modern computer systems use disks as the principle on-line storage medium, for both programs and data. n The operating system is responsible for the following activities in connection with disk management nFree space managementnStorage allocationnDisk scheduling I/O System Managementn The I/O system consists of:nA buffer-caching systemnA general device-driver interfacenDrivers for specific hardware devices File Managementn A file is a collection of related information defined by its creator. Commonly, files represent programs (both source and object forms) and data. n The operating system is responsible for the following activities in connections with file management:n File creation and deletion. n Directory creation and deletion. n Support of primitives原語 for manipulating files and directories.n Mapping files onto secondary storage. n File backup on stable (nonvolatile) storage media. Protection Systemn Protection refers to a mechanism for controlling access by programs, processes, or users to both system and user resources.n The protection mechanism mustn distinguish between authorized and unauthorized usage. n specify the controls to be imposed. n provide a means of enforcement. Networking (Distributed Systems)n A distributed system is a collection processors that do not share memory or a clock. Each processor has its own local memory.n The processors in the system are connected through a communication network.n A distributed system provides user access to various system resources. n Access to a shared resource allows:n Computation speed-up 加速運算n Increased data availability 提高數(shù)據(jù)利用性n Enhanced reliability 增強可靠性 Command-Interpreter Systemn Many commands are given to the operating system by control statements which deal with: n process creation and managementn I/O handlingn secondary-storage management n main-memory managementn file-system accessn protectionn networking Command-Interpreter System (Cont.)n The program that reads and interprets control statements is called variously: n control-card interpreter n command-line interpreter n shell (in UNIX) Its function is to get and execute the next command statement. Chapter 3 Operating-System Structuresn System Componentsn Operating System Servicesn System Callsn System Programsn System Structure n Virtual Machinesn System Design and Implementation Operating System Servicesn Program execution system capability to load a program into memory and to run it. n I/O operations since user programs cannot execute I/O operations directly, the operating system must provide some means to perform I/O.n File-system manipulation program capability to read, write, create, and delete files. n Communications exchange of information between processes executing either on the same computer or on different systems tied together by a network. Implemented via shared memory or message passing. n Error detection ensure correct computing by detecting errors in the CPU and memory hardware, in I/O devices, or in user programs. Additional Operating System Functions Additional functions exist not for helping the user, but rather for ensuring efficient system operations.Resource allocation allocating resources to multiple users or multiple jobs running at the same time.Accounting keep track of and record which users use how much and what kinds of computer resources for account billing or for accumulating usage statistics.Protection ensuring that all access to system resources is controlled. System Callsn System calls provide the interface between a running program and the operating system.n Generally available as assembly-language instructions.n Languages defined to replace assembly language for systems programming allow system calls to be made directly n Three general methods are used to pass parameters between a running program and the operating system. n Pass parameters in registers. n Store the parameters in a table in memory, and the table address is passed as a parameter in a register. n Push (store) the parameters onto the stack by the program, and pop off the stack by operating system. Passing of Parameters As A Table 表格方式的參數(shù)傳遞 Chapter 3 Operating-System Structuresn System Componentsn Operating System Servicesn System Callsn System Programsn System Structure n Virtual Machinesn System Design and Implementation System Calls (Cont.)n Process controln File managementn Device managementn Information maintenancen Communications System Call process controln end, abortn load, executen create process, terminate processn get process attributes, set process attributesn wait for timen wait event, signal event n Allocate and free memory MS-DOS ExecutionAt System Start-up系統(tǒng)啟動Running a Program運行程序 UNIX Running Multiple Programs System Call file managementn create file, delete filen open, closen read, write, repositionn get file attributes, set file attributes System Call device managementn request device, release devicen read, write, repositionn get device attributes, set device attributesn logically attach or detach devices System Call information managementn get time or date, set time or daten get system data, set system datan get process, file, or device attributesn set process, file, or device attributes System Call communicationsn create, delete communication connectionn send, receive messagesn transfer status informationn attach or detach remote devices Communication ModelsMsg Passing Shared Memory Chapter 3 Operating-System Structuresn System Componentsn Operating System Servicesn System Callsn System Programsn System Structure n Virtual Machinesn System Design and Implementation System Programsn System programs provide a convenient environment for program development and execution. They can be divided into:n File manipulationn Status information n File modificationn Programming language supportn Program loading and executionn Communicationsn Application programs Chapter 3 Operating-System Structuresn System Componentsn Operating System Servicesn System Callsn System Programsn System Structure n Virtual Machinesn System Design and Implementation System Structure Layered Approachn The operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface.n With modularity, layers are selected such that each uses functions (operations) and services of only lower-level layers. An Operating System Layer Layered Structure of the THE OSn A layered design was first used in THE operating system.Its six layers are as follows:layer 5: user programs layer 4: buffering for input and outputlayer 3: operator-console device driverlayer 2: memory managementlayer 1: CPU schedulinglayer 0: hardware MicrokernelsWindows NT Client-Server Structure Chapter 3 Operating-System Structuresn System Componentsn Operating System Servicesn System Callsn System Programsn System Structure n Virtual Machinesn System Design and Implementation Virtual Machinesn A virtual machine takes the layered approach to its logical conclusion. It treats hardware and the operating system kernel as though they were all hardware. 虛擬機是層次化的邏輯結(jié)果n A virtual machine provides an interface identical to the underlying bare hardware.n The operating system creates the illusion of multiple processes, each executing on its own processor with its own (virtual) memory. 操作系統(tǒng)創(chuàng)建了多個進程，每個進程在其處理器和（虛擬）內(nèi)存執(zhí)行 Virtual Machines (Cont.)n The resources of the physical computer are shared to create the virtual machines.n CPU scheduling can create the appearance that users have their own processor. n Spooling and a file system can provide virtual card readers and virtual line printers. n A normal user time-sharing terminal serves as the virtual machine operators console. 普通用戶終端成為虛擬機操作員的控制臺 System ModelsNon-virtual Machine Virtual Machine Advantages/Disadvantages of Virtual Machinesn The virtual-machine concept provides complete protection of system resources since each virtual machine is isolated from all other virtual machines. n 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 a physical 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 underlying machine. The Java Virtual Machine Java .class File on Cross Platforms跨平臺的Java .class文件 Java Development Environment Chapter 3 Operating-System Structuresn System Componentsn Operating System Servicesn System Callsn System Programsn System Structure n Virtual Machinesn System Design and Implementation System Design Goalsn User goals operating system should be convenient to use, easy to learn, reliable, safe, and fast. n System goals operating system should be easy to design, implement, and maintain, as well as flexible, reliable, error-free, and efficient. Mechanisms and Policiesn Mechanisms determine how to do something, policies decide what will be done. 機制確定怎樣做，策略決定要做什么n The separation of policy from mechanism is a very important principle, it allows maximum flexibility if policy decisions are to be changed later. System Implementationn Traditionally written in assembly language, operating systems can now be written in higher-level languages.n Code written in a high-level language:n can be written faster. n is more compact. n is easier to understand and debug. n An operating system is far easier to port (move to some other hardware) if it is written in a high-level language. Homeworkn P83 n 3.5n 3.7n 3.13n 3.15