Computers4 Ch2
Download as PPT, PDF0 likes297 views
The document discusses operating systems and utility programs. It describes how operating systems for large computer systems allocate shared resources like the CPU, memory, storage, and printing to allow for multiprogramming and time-sharing. It also explains common utility programs that perform tasks like file management, backup and restore, file compression, disk defragmentation, and providing device drivers.
Computers4 Ch2
- 1. Operating System and Utility Programs Chapter 2 B.M.H
- 2. Computer System Hardware Input device Processor (CPU) Output device Storage (secondary storage) Software System SW Application SW People MIU
- 3. Learning Objectives OS for large computer systems The method of resource allocation Utility Programs MIU
- 4. Mainframes Large, fast and fairly expensive computers Used by business or government to provide centralized storage EX) IBM 4381, 9300, 3090, Cyber 180 MIU
- 5. MIU
- 6. OS for large computers Large computer - mainframes Around about twice as long as PCs Owned by businesses and universities Used by many people at once Present special (sharing) problems Program, CPU, memory, storage, printer OS : take care of these things behind the scenes So that User can share the computer ’ s resources MIU
- 7. Resource Allocation Allocated? Shared resources (Allocate : give something to somebody for special purpose) Resources allocation : the process of assigning computer resources to certain programs MIU
- 8. Resource Allocation Sharing a CPU Sharing a Memory Sharing Storage Resources Sharing Printing Resources MIU
- 9. Sharing the CPU Most computers have a single CPU. All programs must share it. The sharing process Controlled by the OS Two approaches to sharing Multiprogramming Time-sharing Multiprocessing MIU (Resource allocation)
- 10. Multiprocessing The use of a powerful computer with multiple CPUs Multiple programs can run simultaneously , each using its own processor MIU (Resource allocation)
- 11. Multiprogramming Only one Central Processing Unit Two or more programs are executed in the same time frame, concurrently But not exactly at the same instant Taking turns ; one program runs for a while, and then another one runs Event-driven Programs share resources based on events that take place in the programs. MIU (Resource allocation)
- 12. Multiprogramming Implemented by OS through a system of interrupts Interrupts A signal that causes normal program processing to be suspended temporarily. MIU
- 13. Time-Sharing A special case of multiprogramming Time-driven To give each user a time slice The OS doesn ’ t wait for completion of an event At the end of the time slice, the resources are taken away from the user and given to someone else MIU (Resource allocation)
- 14. Sharing Memory Memory management The process of allocating memory to programs and keeping the programs in memory separate from one another Methods Partitions (or regions) Foreground and background Virtual storage MIU (Resource allocation)
- 15. Partitions Some systems simply divide memory into separate areas (partitions or regions) Each of which can hold a program MIU Sharing Memory
- 16. Foreground and Background Large all-purposed computers divide the memory into foreground and background In a time-sharing environment Foreground For programs that have higher priority : Interactive program (with the user at a terminal awaiting response) Receive more CPU time Background For programs with less pressing schedules lower priorities and less CPU time MIU Sharing Memory
- 17. Virtual Storage (1) Many computer systems uses this technique Called virtual memory Virtual : made to appear to exist by the use of computer SW The programs currently being executed are stored on disk , portions of these programs are brought into memory as needed. Memory : real storage Secondary storage : virtual storage MIU Sharing Memory
- 18. Virtual Storage (2) Paging one way of virtual storage the process of dividing a program into equal-size pieces ; called pages storing them in equal-size memory spaces ; called page frames All pages and page frames : the same fixed size (ex. 2 or 4 KB) MIU Sharing Memory Refer to Fig 2-11
- 19. Sharing Storage Resources More than user want to read or write a record from the same disk pack at the same time OS Keeps track of which file is where Responds to commands to manipulate files Keeps track of the Input and output requests Processes them In the order in which they were received Routes any program instruction to read or write a record MIU Resource allocation
- 20. Sharing Printing Resources Spooling A process for sharing a printer Moving data and store it for a short time on a disk before it is printed Each program writes onto a disk each line that is to be printed The disk file is placed into a queue It is printed when the printer becomes available MIU Resource allocation
- 21. Utility Programs File Manager Back up and Restore File Compression Defragmenter Device Drivers
- 22. Utility Programs (1) Most of the resource allocation tasks : done by the OS without user involvement Utility Programs : perform explicit services at the user ’ s request Utility : a piece of computer SW that performs a particular task Part of the system software, not part of the OS. Some utilities are packaged with OSs Others can be purchased separately MIU
- 23. Utility Programs (2) To avoid duplication of effort Backing up Restoring files Compressing files and entire hard disks Locating files Searching computer viruses MIU
- 24. File manager (1) Organize and manage files in a hierarchical directory structure organized in a way that makes sense to you Directory : a named area in storage that can contain files and other directories The newer versions of Windows : Refer to directories as folders MIU Utility Programs
- 25. File manager (2) Functions Enable you to create the directory structure Display lists of files in directories ; to copy, move, rename, and delete files ; and to format and copy diskettes MIU Utility Programs
- 26. Back up and Restore Make backups of entire hard drives or of selected directories Backing up files involves Making duplicate copies Storing them in a safe place These backups could be made to Diskettes, high capacity media (CD, tape) Create the backup files in a specific format to minimize space requirements Needed the restore routine to use them MIU Utility Programs
- 27. File Compression Reduces the amount of space of a file Compressed file Take up less space on disk Take less time to transmit across communication line Must be uncompressed into their original form before using them Ex) PKZIP, WinZip,RAR MIU Utility Programs
- 28. Defragmenter Reorganize the files on the disk so that all files are stored in contiguous locations Ex) Windows : Disk Defragmenter Fragmented: noncontiguous storing because of not enough space. MIU Utility Programs
- 29. Device Drivers (1) Allow the OS to communicate with peripherals Accepts standard commands from the OS Converts them into the proper format for the device it supports MIU Utility Programs
- 30. Device Drivers (2) Manufactures Provide device drivers for their products Installing the product : includes copying the appropriate driver to your hard drive MIU Utility Programs