240-323 OS,2000

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240-323, Part I Operating - System

Structures

Department of Computer Engineering, PSU Wannarat Suntiamorntut

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Components

• Process Management - process : a program in execution, job - process needs certain resources : CPU time, memory file, I/O device - process is not program!!! - program is a passive entity, whereas a process is an active entity. - process is unit of work in system :

--> Operating system process--> User process

240-323 OS,2000

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System Components

- Os is responsible for the following activities :

* created/deleted processes * mange resource requirements of a process

during its execution : CPU time, memory, I/O, ... * avoid interface between process * achieve cooperation between process

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Components

• Main-Memory Management

- Keep track of which parts of memory are currently being used and by whom.

- Decide which processes are to be loaded into memory when memory space becomes available.

- Allocate and deallocate memory space as needed.

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Components

• File Management

- Created/ deleted files or directories- map files onto secondary storage- backup files on stable storage media- manipulate files or directories

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Components

• I/O System Management

- memory management component includingbuffering, caching, and spooling.

- general device-driver interface- drivers for specific hardware devices

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Components

• Secondary-Storage Management

- Free-space management- Storage allocation- Disk scheduling

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Components

• Networking

Distributed system is a collection of processorsthat has its own local memory and clock, communicatewith one another through various lines.

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Components

• Protection System

Controlling the access of programs, processes or users to the resources defined by computer system.

• Command-Interpreter System- Interface between user and OS.- As same as command-line interpreter (shell).- Get next command statement and execute it.

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

Operating-System Services

OS services are provided for the convenience of programmer.• Program execution

System loads program into main memory,executes, and terminate (abnormal, normal).• I/O Operations

files or I/O devices• File-system manipulation

Copy or delete files• Communication

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

Operating-System Services

OS services are provided for multiusers• Resource allocation

CPU cycle, main memory, file storage, I/O• Accounting

status of user• Protection

Information for each users, Security

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Calls

• System call provided directed access to OS by programmers (assembly).• System call can be used from high level languages suchas copy file use :- Interactive system must be work in sequence.- bath system to define the parameter (file name)

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Calls : Copy file

Start Receive names of files Prompt messg

Read characterPut in parameterPass para.

Open fileError

Loop read input file Write output

Close both fileTerminate normally

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System Calls

• System call can provided into- process control- file manipulation- device manipulation- information manipulation- communications

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

System structure

• Simple Structure : small, simple and limited systems

Application Program

Resident system program

MS-DOS device drivers

ROM BIOS device drivers

240-323 OS,2000

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Department of Computer Engineering, PSU Wannarat Suntiamorntut

UNIX System structure

USERSShell and commands compilers and interpreters system libraries

System call interface to kernel

Signals terminalhandlingcharacter I/O systemterminal drivers

File systemswapping block I/O systemdisk and tape

CPU schedulingpage replacementdemand pagingvirtual memory

Kernel interface to kernel

Terminal controller device controller memory controller disk and tape