1. Introduction to Computing Lecture # 5 Introduction to Computing Lecture # 5

2. 2 Outline System software and its components Operating system and its functions Device drivers and utility programs

3. 3 System Software System software enables the applications software to interact with the computer and helps the computer manage its internal and external resources. (Williams & Sawyer) System software is a collection of computer programs that manage the resources of a computer and facilitate access to those resources. (Schneider & Gersting) There are three basic components of system software: 1. Operating systems 2. Device drivers 3. Utility programs

4. 4 The Components of System Software 1.Operating system - the principal component of system software 2.Device drivers - help the computer control peripheral devices 3.Utility programs - support, enhance, or expand existing programs

5. 5 The Operating System: What It Does The operating system consists of the master system of programs that manage the basic operations of the computer. These programs provide resource management services of many kinds. They handle the control of and use of hardware resources: –Disk space –Memory –CPU –Peripheral devices

6. 6 The Operating System: What It Does Booting - the process of loading an operating system into a computer’s main memory

7. 7 The Operating System: What It Does Booting –diagnostic routines first start up and test the main memory, the central processing unit, and other parts of the system to make sure they are running properly. –BIOS (basic input/output system) will be copied to main memory to help the computer interpret keyboard characters or transmit characters to the display screen or to a diskette. –Then the boot program obtains the operating system, usually from hard disk, and loads it into the computer’s main memory.

8. 8 The Operating System: What It Does OS provides user interface: user-controllable display screen that allows you to interact with your computer

9. 9 The Operating System: What It Does CPU Management Supervisor (kernel) – manages the CPU. It remains in main memory while the computer is running, and directs other “non-resident” programs to perform tasks that support application programs. Example –Writing a report using a word processor program and want to print out a portion of it while continuing to write. –OS will select a printer –Executing printer driver

10. 10 The Operating System: What It Does Memory Management The OS manages memory via: –Partitioning - division of memory into separate areas called partitions, each of which can hold a program or data. –Foreground/background - division of memory into higher priority (foreground) and lower priority (background) areas. –Queues - temporary line-ups for programs waiting to be executed. Programs that are to be executed wait on disk in queues.

11. 11 The Operating System: What It Does File Management A file is a named collection of related information. A file can be a program or it can be a data file. Files are stored on hard disks and other secondary storage devices. OS records the storage location of all files.

12. 12 The Operating System: What It Does Task Management A task is an operation such as storing, printing or calculating. A computer is required to perform many different tasks at once. Some operating systems also handle more than one program at the same time. Among the ways operating systems manage tasks in order to run more efficiently are: –Multitasking –Multiprogramming –Time sharing –Multiprocessing

13. 13 The Operating System: What It Does Task Management Multitasking –Multitasking is the execution of two or more programs by one user concurrently on the same computer with one CPU. –Executing more than one program concurrently. –Earlier OS could do only single-tasking –Today, multitasking Operating Systems are used. –OS directs the processor to spend a predetermined amount of time executing the instructions for each program, one at a time. –A small part of each program is executed, and the cycle keeps on repeating until processing is complete.

14. 14 The Operating System: What It Does Task Management Multiprogramming –Multiprogramming is the execution of different users’ programs concurrently on a multi-user operating system. –Concurrent execution of different users’ programs –The processor spends a certain amount of time executing each user’s program.

15. 15 The Operating System: What It Does Task Management Time sharing –In time-sharing, a single computer processes the tasks of several users at different stations in round- robin fashion. –Round-robin processing of programs for several users. –Time slicing is used for time sharing. –A time slice is a fraction of a second. –The computer may rapidly switch back and forth among different tasks.

16. Introduction to Computing Lecture # 5 Introduction to Computing Lecture # 5

17. 17 The Operating System: What It Does Task Management Multitasking The processor directs the programs to take turns accomplishing small tasks or events, such as, a calculation, search a record, print a part. Each task may take a different amount of time. Time-sharing The computer spends a fixed amount of time with each program before going on to the next one. Multitasking Vs Time-sharing

18. 18 The Operating System: What It Does Task Management Multiprocessing –Multiprocessing is processing done by two or more computers or processors linked together to perform work simultaneously. –Simultaneous processing of two or more programs by multiple computers –Processing instructions from different programs or different instructions within the same program at once.

19. 19 The Operating System: What It Does Task Management Two possible approaches to multiprocessing: –Coprocessing - the controlling CPU works together with specialized microprocessors called coprocessors, each of which handles a particular task. –Parallel processing - several full-fledged processors work together on the same tasks, sharing memory.

20. 20 The Operating System: What It Does Task Management Number of Users Number of Processors Order of Processing Multi-taskingOne Concurrently Multi- programming MultipleOneConcurrently Time sharingMultipleOneRound robin Multi- processing One or moreTwo or moreSimultaneously Processing of two or more programs

21. 21 The Operating System: What It Does Formatting (initializing) a disk - the process of preparing that disk so that it can store data or programs

22. 22 Other System Software: Device Drivers & Utility Programs Device drivers - specialized software programs that allow input and output devices to communicate with the rest of the computer system

23. 23 Other System Software: Device Drivers & Utility Programs Many basic device derivers come with system software. If, however, we buy a new peripheral device, such as a mouse, scanner, or printer, the package will include a device driver (probably on a CD-ROM).

24. 24 Utilities: Service Programs Utility Programs, also known as service programs, perform tasks related to the control and allocation of computer resources. They enhance existing functions or provide services not supplied by other system software programs. Built-in utilities – as part of the operating system. External utility programs – such as Norton Desktop

25. 25 Utilities: Service Programs Backup utility –Program which makes a duplicate copy of the information onto hard disk or removable media. –Example: Norton Backup

26. 26 Utilities: Service Programs Data-recovery utility –Program which restores data that has been physically damaged or corrupted. –Data can be damaged by viruses, bad software, hardware failure, and power fluctuations that occur while data is being written/recorded.

27. 27 Utilities: Service Programs Virus –A virus consists of hidden programming instructions that are buried within an application or system program. –They copy themselves to other programs, causing destruction. –Viruses are spread when people exchange floppy disks or download information from computer networks or the Internet

28. 28 Utilities: Service Programs Antivirus software –Program that scans hard disks, floppy disks, and memory to detect viruses. –Some utilities destroy the virus as soon as it is detected and others notify the user of possible viral behavior. –Examples of antivirus software are Norton AntiVirus, Dr. Solomon’s Anti-Virus Toolkit, McAfee VirusScan, and Webscan.

29. 29 Utilities: Service Programs Data compression utility –In order to gain more disk space, the user has four options: delete old files buy a new hard disk with more capacity add an hard drive or buy a data compression utility. –Program which removes redundant elements, gaps, and unnecessary data from a computer’s storage space so that less space (fewer bits) is required to store or transmit data.

30. 30 Utilities: Service Programs Fragmentation - the scattering of portions of files about the disk in nonadjacent areas, thus greatly slowing access to the files Defragmenter utility - program that finds all the scattered files on your hard disk and reorganizes them as contiguous files

31. 31 Utilities: Service Programs Disk scanner and disk cleanup utilities: Detect & remove unnecessary files Detect & correct disk problems