OS, , Part I Operating - System Structures Department of Computer Engineering, PSUWannarat Suntiamorntut

OS, Department of Computer Engineering, PSUWannarat 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

OS, Department of Computer Engineering, PSUWannarat Suntiamorntut 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

OS, Department of Computer Engineering, PSUWannarat 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.

OS, Department of Computer Engineering, PSUWannarat 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

OS, Department of Computer Engineering, PSUWannarat Suntiamorntut System Components I/O System Management - memory management component including buffering, caching, and spooling. - general device-driver interface - drivers for specific hardware devices

OS, Department of Computer Engineering, PSUWannarat Suntiamorntut System Components Secondary-Storage Management - Free-space management - Storage allocation - Disk scheduling

OS, Department of Computer Engineering, PSUWannarat Suntiamorntut System Components Networking Distributed system is a collection of processors that has its own local memory and clock, communicate with one another through various lines.

OS, Department of Computer Engineering, PSUWannarat 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.

OS, Department of Computer Engineering, PSUWannarat 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

OS, Department of Computer Engineering, PSUWannarat 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

OS, Department of Computer Engineering, PSUWannarat Suntiamorntut System Calls System call provided directed access to OS by programmers (assembly). System call can be used from high level languages such as copy file use : - Interactive system must be work in sequence. - bath system to define the parameter (file name)

OS, Department of Computer Engineering, PSUWannarat Suntiamorntut System Calls : Copy file StartReceive names of filesPrompt messg Read character Put in parameter Pass para. Open file Error Loop read input file Write output Close both file Terminate normally

OS, Department of Computer Engineering, PSUWannarat Suntiamorntut System Calls System call can provided into - process control - file manipulation - device manipulation - information manipulation - communications

OS, Department of Computer Engineering, PSUWannarat Suntiamorntut System structure Simple Structure : small, simple and limited systems Application Program Resident system program MS-DOS device drivers ROM BIOS device drivers

OS, Department of Computer Engineering, PSUWannarat Suntiamorntut UNIX System structure USERS Shell and commands compilers and interpreters system libraries System call interface to kernel Signals terminal handling character I/O system terminal drivers File system swapping block I/O system disk and tape CPU scheduling page replacement demand paging virtual memory Kernel interface to kernel Terminal controller device controllermemory controller disk and tape