Copyright © 2003 by Prentice Hall 1 Computers: Tools for an Information Age Chapter 3 Operating Systems: Software in the Background BSM025 Computers

2Copyright © 2003 by Prentice Hall Objectives Describe the functions of an operating system Explain the basics of a personal computer operating system Describe the advantages of a graphical operating system Differentiate among different versions of Microsoft Windows Explain the need for network operating systems

3Copyright © 2003 by Prentice Hall Objectives Describe the methods of resource allocation on large computers Describe the differences among multiprocessing, multiprogramming, and time-sharing Explain the principles of memory management List several functions that are typically performed by utility programs

4Copyright © 2003 by Prentice Hall Operating Systems: Hidden Software Serves as intermediary between hardware and applications software Operating System Operating System Systems software Systems software Kernel

5Copyright © 2003 by Prentice Hall Operating System A set of programs that lies between applications software and the hardware Manages computer’s resources (CPU, peripheral devices) Manages computer’s resources (CPU, peripheral devices) Establishes a user interface Establishes a user interface Determines how user interacts with operating system Provides and executes services for applications software Provides and executes services for applications software Return

6Copyright © 2003 by Prentice Hall Systems Software All programs related to coordinating computer operations Examples Operating systems Operating systems Language translators Language translators Convert program code to machine-readable form Utility programs Utility programs Perform secondary chores Return

7Copyright © 2003 by Prentice Hall Kernel Manages the operating system Loaded from hard drive into memory when computer is booted Loaded from hard drive into memory when computer is booted Booting refers to starting the computer Loads other operating system programs from disk storage as needed Loads other operating system programs from disk storage as needed Other programs referred to as nonresident Return

8Copyright © 2003 by Prentice Hall Operating Systems for Personal Computers Platform: combination of computer hardware and operating system software Wintel (Microsoft Windows running on an Intel-based PC) is most common Wintel (Microsoft Windows running on an Intel-based PC) is most common Common Platforms MS-DOS MS-DOS MS-DOS Windows Windows Windows MAC OS MAC OS MAC OS MAC OS Unix Unix Unix Linux Linux Linux

9Copyright © 2003 by Prentice Hall MS-DOS Uses a command-line interface Screen provides prompts for user Screen provides prompts for user User types commands User types commands Largely replaced by graphical user interfaces Not user-friendly Return

10Copyright © 2003 by Prentice Hall Microsoft Windows Began as an operating environment for MS- DOS operating environment operating environment Not a full-blown operating system; required MS- DOS Not a full-blown operating system; required MS- DOS Uses a graphical user interface graphical user interfacegraphical user interface Users can use DOS commands and interface Users can use DOS commands and interface Now a complete family of operating systems complete familycomplete family Return

11Copyright © 2003 by Prentice Hall Graphical User Interface User clicks an icon to perform tasks Start Menu in lower left corner launches programs Use menus to activate commands Return

12Copyright © 2003 by Prentice Hall Windows Features Long file names (up to 255 characters) Plug and Play Makes installing hardware components easier Makes installing hardware components easier Object Linking and Embedding (OLE) Allows user to embed or link one document to another Allows user to embed or link one document to another Return

13Copyright © 2003 by Prentice Hall Windows XP Brings consumer and corporate versions of Windows together into a single product Has Home and Professional Editions Has Home and Professional Editions Enhancements Return

14Copyright © 2003 by Prentice Hall Windows XP Enhancements Improved user interface Much clearer and uncluttered desktop Much clearer and uncluttered desktop More icons on redesigned Start Menu More icons on redesigned Start Menu Improved multimedia support More personalization Multiple user support User can log off, leaving programs running, and allow another user to log on User can log off, leaving programs running, and allow another user to log on Set up limited accounts for children to use; i.e., no inappropriate games or no Internet access Set up limited accounts for children to use; i.e., no inappropriate games or no Internet access Internet support and protection Return

15Copyright © 2003 by Prentice Hall UNIX Developed in 1971 for use on the DEC minicomputer Character-based system with command-line interface Not tied to any family of processors Runs on just about every type of system (PC, mainframe, workstation) from any manufacturer Runs on just about every type of system (PC, mainframe, workstation) from any manufacturer Primary operating system in use on Internet servers Handles many simultaneous users easily Handles many simultaneous users easily Return

16Copyright © 2003 by Prentice Hall Network Functions Sharing resources (hard disks and printers) Data security Troubleshooting Administrative control Return

17Copyright © 2003 by Prentice Hall Sharing the CPU Multiprocessing Multiprogramming Time-Sharing Return

18Copyright © 2003 by Prentice Hall Multiprocessing The use of a powerful computer with multiple CPUs Multiple programs run simultaneously Each runs on its own processor Each runs on its own processor Return

19Copyright © 2003 by Prentice Hall Multiprogramming Two or more programs executed concurrently Programs take turns using the CPU Programs take turns using the CPU Event-driven Event-driven An interrupt suspends processing to allow another program to run After the second program runs, the operating system returns the CPU to another program Generally used for batch programs that do not require user input Return

20Copyright © 2003 by Prentice Hall Time-Sharing Programs take turns using the CPU Time-driven Each user is given a slice of time (fraction of a second) Each user is given a slice of time (fraction of a second) CPU works only on that user’s tasks during its time slice CPU works only on that user’s tasks during its time slice Response time: the time between typed request and computer’s reply Response time: the time between typed request and computer’s reply Typically used in applications with many users Return

21Copyright © 2003 by Prentice Hall Utility Programs Perform secondary chores Examples File manager File manager File manager File manager File compression File compression File compression File compression Others Others Others

22Copyright © 2003 by Prentice Hall File Manager Stores files in a hierarchical directory structure Windows uses Windows Explorer Return

23Copyright © 2003 by Prentice Hall File Compression Reduces amount of space a file requires Makes file take up less space on disk Makes file take up less space on disk Takes less time to transmit across communication lines Takes less time to transmit across communication lines Return

24Copyright © 2003 by Prentice Hall Other Utility Programs Backup and Restore Backup: make copies of disks and store in a safe place Backup: make copies of disks and store in a safe place Restore: restore files from backups Restore: restore files from backups Disk defragmenter: reorganizes disk so all files are stored in contiguous locations Device driver: handles commands for devices, such as printers and storage devices Return