Department of Computer Engineering PSU Wannarat Suntiamorntut 240

Department of Computer Engineering, PSU Wannarat Suntiamorntut 240 -323, Part I Operating - System Structures 240 -323 OS, 2000 1

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 2

Department of Computer Engineering, PSU Wannarat 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 240 -323 OS, 2000 3

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 4

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 5

Department of Computer Engineering, PSU Wannarat Suntiamorntut System Components • I/O System Management -memory management component including buffering, caching, and spooling. -general device-driver interface -drivers for specific hardware devices 240 -323 OS, 2000 6

Department of Computer Engineering, PSU Wannarat Suntiamorntut System Components • Secondary-Storage Management -Free-space management -Storage allocation -Disk scheduling 240 -323 OS, 2000 7

Department of Computer Engineering, PSU Wannarat 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. 240 -323 OS, 2000 8

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 9

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 10

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 11

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 such as copy file use: -Interactive system must be work in sequence. -bath system to define the parameter (file name( 240 -323 OS, 2000 12

Department of Computer Engineering, PSU Wannarat Suntiamorntut System Calls : Copy file Start Pass para. Open file Receive names of files Put in parameter Read character Error Loop read input file Terminate normally 240 -323 OS, 2000 Prompt messg Write output Close both file 13

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 14

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 15

Department of Computer Engineering, PSU Wannarat Suntiamorntut UNIX System structure USERS Shell and commands compilers and interpreters system libraries System call interface to kernel Signals terminal File system handling swapping block character I/O system terminal drivers disk and tape CPU scheduling page replacement demand paging virtual memory Kernel interface to kernel Terminal controller 240 -323 OS, 2000 device controller disk and tape memory controller 16