1、Operating System Concepts,Chapter 3: Operating-System Structures,System Components Operating System Services System Calls * System Programs System Structure,Operating System Concepts,3.1 System Components,Many modern operating systems support the system components as following. Process Management Ma

2、in Memory Management File Management I/O System Management Secondary Management Networking Protection System Command-Interpreter System,Operating System Concepts,3.1 System Components (1),A process is a program in execution. A process needs certain resources - including CPU time, memory, files, and

3、I/O devices - to accomplish its task. What are the differences between process and program? Operating system is responsible for the following actions in connection with process management. Process creation and deletion. Process suspension and resumption. Providing mechanisms for process synchronizat

4、ion and process communication Providing mechanisms for deadlock handling,-Process Management,Operating System Concepts,3.1 System Components (2),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. Main

5、 memory is generally the only large storage device that the CPU can address and access directly. Main memory is a volatile storage device. It loses its contents in the case of system failure. Operating system is responsible for the following activities in connections with memory management: Keep tra

6、ck of which parts of memory are currently being used and by whom. Decide which processes to load when memory space becomes available. Allocate and deallocate memory space as needed.,- Main-Memory Management,Operating System Concepts,3.1 System Components (3),A file is a collection of related informa

7、tion defined by its creator. Commonly, files represent programs ( both source and object forms) and data. The OS implements the abstract concept of a file by managing mass storage media and the devices that control them. Flies are normally organized into directories to ease their use. The operating

8、system is responsible for the following activities in connection with file management: File creation and deletion. Directory creation and deletion. Support of primitives for manipulating files and directories. Mapping files onto secondary storage. File backup on stable (nonvolatile) storage media.,-

9、 File Management,Operating System Concepts,3.1 System Components (4),One of the purposes of OS is to hide the peculiarities of specific hardware devices from user. The peculiarities of I/O devices are hidden from the bulk of the OS itself by the I/O subsystem. The I/O system consists of: A buffer-ca

10、ching system A general device-driver interface Drivers for specific hardware devices Only the device driver knows the peculiarities of the specific device to which it is assigned.,- I/O System Management,Operating System Concepts,3.1 System Components (5),Since main memory (primary storage) is volat

11、ile and too small to accommodate all data and programs permanently, the computer system must provide secondary storage to back up main memory. Most modern computer systems use disks as the principle on-line storage medium, for both programs and data. The operating system is responsible for the follo

12、wing activities in connection with disk management: Free space management Storage allocation Disk scheduling,- Secondary-Storage Management,Operating System Concepts,3.1 System Components (6),A distributed system is a collection of processors that do not share memory or a clock. Each processor has i

13、ts own local memory and clock. The processors in the system are connected through a communication network. Communication takes place using a protocol. A distributed system provides user access to various system resources. Access to a shared resource allows: Computation speed-up Increased data availa

14、bility Enhanced reliability,- Networking (Distributed Systems),Operating System Concepts,3.1 System Components (7),Protection refers to a mechanism for controlling access by programs, processes, or users to both system and user resources. The protection mechanism must: distinguish between authorized

15、 and unauthorized usage. specify the controls to be imposed. provide a means of enforcement.,- Protection System,Operating System Concepts,3.1 System Components (8),Command-interpreter is the interface between the user and the operating system. Some OS include the command-interpreter in the kernel w

16、hile others as a special program. The program that reads and interprets control statements is called variously: command-line interpreter shell (in UNIX) Its function is to get and execute the next command statement.,- Command-Interpreter System,Operating System Concepts,3.1 System Components (9),Man

17、y commands are given to the operating system by control statements which deal with: process creation and management I/O handling secondary-storage management main-memory management file-system access protection networking,- Command-Interpreter System,Operating System Concepts,3.2 Operating System Se

18、rvices,Commonly, the OS provides the following services for programmer to make the programming task easier. Program execution system capability to load a program into memory and to run it. I/O operations since user programs cannot execute I/O operations directly, the operating system must provide so

19、me means to perform I/O. File-system manipulation program capability to read, write, create, and delete files. Communications exchange information between processes executing either on the same computer or on different systems tied together by a network. Implemented via shared memory or message pass

20、ing. Error detection ensure correct computing by detecting errors in the CPU and memory hardware, in I/O devices, or in user programs.,Operating System Concepts,3.2 Operating System Services (1),Additional functions exist not for helping the user, but rather for ensuring efficient system operations.

21、 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 sy

22、stem resources is controlled.,Operating System Concepts,3.3 System Calls,*System calls provide the interface between a running program and the OS. Generally available as assembly-language instructions. Languages defined to replace assembly language for systems programming and allow system calls to b

23、e made directly (e.g., C, C+) Run-time support system (the set of functions built into libraries included with a compiler) for most programming languages provides a much simple interface.,Operating System Concepts,3.3 System Calls (1),Three general methods are used to pass parameters from a running

24、program to the operating system system calls. Pass parameters in registers. Store the parameters in a table in memory, and the table address is passed as a parameter in a register. (taken by Linux) Push (store) the parameters onto the stack by the program, and pop off the stack by operating system.,

25、Operating System Concepts,3.3 System Calls (2),Passing of parameters as a table,Operating System Concepts,3.3 System Calls (3),Types of System Calls Process control end, abort; load, execute; create, terminate; get/set attributes; wait for time; wait event, signal event; allocate and free memory. Fi

26、le management create/delete; open/close; read, write, reposition; get/set attributes. Device management request/release device; read, write reposition; get/set attributes; logically attach or detach devices. Information maintenance get/set time or date; get/set system data; get/set process, file, or

27、 device attributes. Communications create/delete communication connection; send/receive message; transfer status information; attach or detach remote devices.,Operating System Concepts,Communication Models,Communication may take place using either message passing or shared memory.,Operating System C

28、oncepts,3.4 System Programs,System programs provide a convenient environment for program development and execution. Some of them are simply user interfaces to system calls. They can be divided into: File manipulation Status information File modification Programming language support Program loading a

29、nd execution Communications Most users view of the operation system is defined by system programs, not the actual system calls.,Operating System Concepts,3.4 System Programs (1),The most important system program for an OS is the command interpreter. Application programs solve common problems or perf

30、orm common operations, also system utilities. Such as web browsers, word processors, spreadsheets Also include programs made by users Database systems is application programs?,Operating System Concepts,Components of a computer system,Operating System Concepts,3.5 System Structure,MS-DOS written to p

31、rovide the most functionality in the least space, because of the limited hardware on which it ran. not divided into modules Although MS-DOS has some structure, its interfaces and levels of functionality are not well separated,- Simple Structure,Operating System Concepts,MS-DOS Layer Structure,Operat

32、ing System Concepts,3.5 System Structure (1),UNIX another limited by hardware functionality, the original UNIX operating system had limited structuring. It consists of two separable parts. Systems programs The kernel Consists of everything below the system-call interface and above the physical hardware Provides the file system, CPU scheduling, memory management, and other operating-system functions; a large number of functions for one level. An enormous of functionality to be combined into o level. This makes UNIX difficult to enhance, as c