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Tonga Institute of Higher Education IT 141

Tonga Institute of Higher Education IT 141. Lecture 5: Operating System. Operating System (OS). Type of software that acts as the master controller for all activities that take place within a computer system E.g. – Microsoft Windows, Mac OS, Linux, DOS, UNIX, Solaris, and BeOS.

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Tonga Institute of Higher Education IT 141

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  1. Tonga Institute of Higher EducationIT 141 Lecture 5: Operating System

  2. Operating System (OS) • Type of software that acts as the master controller for all activities that take place within a computer system • E.g. – Microsoft Windows, Mac OS, Linux, DOS, UNIX, Solaris, and BeOS

  3. What does an OS do?

  4. What does an OS do?

  5. OS Tasks • Manage processor resources • Manage memory • Keep track of storage resources • Ensure that input and output proceed in an orderly manner • Establish basic elements of the user interface

  6. How OS manage processor resources • Processes – activities • Processes compete for your computer’s microprocessor’s attention • OS must ensure that each process receives its share of microprocessor cycles

  7. OS handling so many processes Can be managed by • Multitasking • Multithreading • Multiprocessing

  8. OS managing memory • Microprocessor works with data and executes instructions stored in RAM • OS divide up specific areas of memory for each program • Prevents a memory leak. • Use Ctrl+Alt+Del key to close corrupted programs

  9. OS keeping track of storage resources • Acts as a filing clerk • Remembers names and locations of files • Keeps track of empty spaces

  10. OS and peripheral devices • OS communicates with device driver software so that data travel smoothly between computer and peripheral devices • OS makes sure that input and output continue in an orderly manner • Buffers collect and hold data when busy • Buffer – part of memory that holds data waiting to be transferred from one device to another

  11. Different OS needed for different computing tasks • Single-user OS – deal with one set of input devices. E.g. DOS • Multiuser OS – allows a single, centralized computer to deal with simultaneous input, output, and processing requests from many users. E.g. – IBM’s z/OS • Server OS – provides tools for managing distributed works, e-mail servers, and Web hosting sites. E.g. – Mac OS X Server, Windows Server 2008 • Desktop OS – designed for a PC. E.g. – Microsoft Windows or Mac OS

  12. Interacting directly with OS • When you start your computer • Manage files (Windows Explorer): allows you to view, move, copy, rename or delete • Get help • Customize interface: help you customize your screen display and work environment • Configure equipment: access and utilities to help set up and configure computer’s hardware and peripheral devices

  13. User Interfaces • Definition: mixture of hardware and software that helps people and computers communicate with each other • OS defines the look and feel of compatible software • Know what • Icon, desktop, window, taskbar, toolbar, ribbon, menu, submenu, tab, etc.

  14. Windows, Mac OS, and Linux similar? • They differ in their visual design

  15. Boot Process • Digital devices – OS is stored in ROM • Larger devices – OS is quite large, stored in hard disk • Boot process – operating system kernel loaded into RAM • Kernel provides key OS services such as memory management and file access. • Kernel stays in RAM all the time your comp is on. • Other OS parts are only loaded when needed

  16. Boot Process • Steps of events that happen between the time you turn on the comp, and the time it is ready for you to issue commands • Bootstrap program is built into special ROM chip in the computer’s system unit. When it receives power, it starts the boot processing by executing the bootstrap program.

  17. Boot process major events • Power up • Start boot program • Power-on self-test • Identify peripheral devices • Load operating system • Check configuration and customization

  18. OS in hard disks • Because RAM is volatile, we can’t store OS in hard disks. ROM and EEPROM are non-volatile, and can still store data even when the power is off, but too small for OS. • During booting, OS is transferred into RAM

  19. 6 major events during the boot process • Power up • Start boot program • power-on self test • Identify peripheral devices • Load OS • Check configuration and customization

  20. Why OS is stored in HD not RAM • Because RAM is volatile • EEPROM and ROM are non volatile but their storage capacity are not big enough • OS is transferred to RAM for quick access

  21. Bootstrap summary

  22. Microsoft Windows OS • Microsoft Windows (Windows 1.0, Windows 2.0……Windows 2008) • Adv: variety of hardware platforms, user community, gives excellent support in the form of built-in drivers and plug and play funcitonality • Disadv: reliability and security • There are different Microsoft windows for different computer categories

  23. Microsoft Windows versions

  24. MAC OS • Macintosh OS • For Apple Computer’s Macintosh line of computer systems • Classic Mac OS, System 6, System 7/Mac OS,…. Mac OS X 10.5 (Leopard) • Adv: easy to use, reliable, and secure. Offers strong backward compatibility, dual boot options, and good virtual machine platform • Disadv: limited selection of software

  25. UNIX and LINUX OS • Linux developed based on a UNIX derivative called MINX • Linux adv: distributed with source code for everyone to use. • Disadv: mostly for technical users

  26. DOS (Disk Operating System) • First OS and old, developed by Microsoft • Command-line user interface

  27. Handheld Operating System • Palm OS, Windows Mobile OS, iPhone OS X, Symbian OS • OS for handheld and desktop gives similar services but handheld devices are simpler therefore their OS are simpler and smaller. The OS can be stored in ROM.

  28. File Basics • File – named collection of data that exists on a storage medium • File-naming conventions. Each OS has a unique set of rules. Max length for naming files is 255 characters. • File name extension – optional file identifier separated from the main file by a period (E.g. pain.exe, .dat – document, .doc – word processing

  29. File Basics • Reserved words – words used as commands or special identifiers that you CANNOT USE as a file name (e.g. – Nul, Aux, Com1, Com2, Con, Lpt1, Lpt 2) • Some OS are case sensitive. Upper and Lowercase letters.

  30. File Directories and folders • You can choose a file’s location • Disk partition – section of a hard disk drive that is treated as a separate storage unit. Can be assigned drive letters. Partition C, or D. It is NOT like folders. It is more permanent, and a special utility is required to create, modify, or delete them

  31. File Directories and folders • Directory – list of files for each storage disk • Root directory – main directory • Subdirectory – smaller list subdivided from the root director • Folder • File specification (Path) – includes the drive letter, folder(s), file name, and extension.

  32. File Directories and folders • File size – measured in bytes • OS keeps track of file sizes and supplies that information when you ask the list of the files • File date • File format – organization and layout of data that is stored in a file. • File header – section of data at the beginning of a file (date created, date updated, size, file type)

  33. FILE FORMATS (OS and Executable Extensions)

  34. Data File Extensions

  35. Why can’t I open files • File damaged • Someone changed the file extension • Some file formats exist in several variations, and your software might have the capability to open a particular variation of the format.

  36. Converting a file from one format to another • Easiest way to convert a file • Open the file using that software, and then use the Export option, or Save As dialog box, to select a new file format, assign the file a new name and save it. • Some conversions DO NOT keep all the characteristics of the original file.

  37. FILE MANAGEMENT • OS helps you organize and manipulate your files from • within an application program • or by using a SPECIAL FILE MANAGEMENT UTILITY

  38. Application-based file management • Apps provide a way to open files and save them in a specific folder in designated storage device • Some apps allow you to tag a file. File tag in Windows is a piece of information that describes the file

  39. Save and Save As Option Save As Option allows you to select a name and storage device for a file, whereas the Save option simply saves the latest version of a file under its current name and its current location

  40. Save As option • Using apps, software interact with OS’s file management system when you’re opening and saving files • OS needs to know the name of a newly created file • Apps checks with the OS to get list of available files (searching)

  41. FILE MANAGEMENT UTILITIES • OS provide file management utilities that shows you the files stored on your disks and lets you work with them • Mac OS X – Finder • Windows Vista – Explorer Helps you view a list of files, find files, move files from one place to another, make copies of files, delete files, discover file properties, and rename files.

  42. FILE MANAGEMENT METAPHORS • Logical storage models – metaphors that help you form a mental (logical) picture of the way in which files are stored • Filing cabinet • Tree structure Microsoft programmer combined the filing cabinet metaphor with the tree structure metaphor in the WINDOWS EXPLORER FILE MANAGEMENT UTILITY

  43. Tree Structure

  44. Windows Explorer

  45. Physical File Storage • OS help you visualize computer storage as files and folders • Physical storage model describes what really happens on the disks and in circuits • Before storing, the storage medium must be formatted • Formatting: process of dividing disk into tracks and sectors

  46. Tracks and Sectors

  47. OS keeping track of a file’s location • OS uses file system. Different systems use different file systems • Mac OS: Macitonsh Hierarchical File System Plus (HFS+) • Linux: Ext3fs (third extended file system) • Windows NT, 2000, Vista: New Technology File System (NTFS) Windows 95, 98, Me: FAT32

  48. OS keeping track of a file’s location • To speed up the process of storing and retrieving data, a disk drive usually works with group of sectors called cluster or a “block”. • The number of sectors that form a cluster varies • A file system primary task is to maintain a list of clusters and keep track of which are empty and which hold data.

  49. OS keeping track of a file’s location • This information is stored in a special index file • FAT32 file system: index file is called File Allocation table (FAT) • NTFS file system: index is called Master File Table (MFT) • If MFT or FAT is damaged or corrupted data can be lost. Important to backup.

  50. OS keeping track of a file’s location • When you save a file, the operating system looks at the file allocation table to see what cluster is free. • Then it will update the allocation table to indicate that the file is saved in that cluster • If the file is too big to fit in one cluster, it will use more clusters that are next to it

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