tonga institute of higher education it 141

Tonga Institute of Higher Education IT 141

Tonga Institute of Higher EducationIT 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 systemE.g. Microsoft Windows, Mac OS, Linux, DOS, UNIX, Solaris, and BeOS

What does an OS do?

What does an OS do?

OS Tasks
Manage processor resourcesManage memoryKeep track of storage resourcesEnsure that input and output proceed in an orderly mannerEstablish basic elements of the user interface

How OS manage processor resources
Processes activitiesProcesses compete for your computers microprocessors attentionOS must ensure that each process receives its share of microprocessor cycles

OS handling so many processes
Can be managed by Multitasking MultithreadingMultiprocessing

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

OS keeping track of storage resources
Acts as a filing clerkRemembers names and locations of filesKeeps track of empty spaces

OS and peripheral devices
OS communicates with device driver software so that data travel smoothly between computer and peripheral devicesOS makes sure that input and output continue in an orderly mannerBuffers collect and hold data when busyBuffer part of memory that holds data waiting to be transferred from one device to another

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

Interacting directly with OS
When you start your computerManage files (Windows Explorer): allows you to view, move, copy, rename or deleteGet helpCustomize interface: help you customize your screen display and work environmentConfigure equipment: access and utilities to help set up and configure computers hardware and peripheral devices

User Interfaces
Definition: mixture of hardware and software that helps people and computers communicate with each otherOS defines the look and feel of compatible softwareKnow whatIcon, desktop, window, taskbar, toolbar, ribbon, menu, submenu, tab, etc.

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

Boot Process
Digital devices OS is stored in ROMLarger devices OS is quite large, stored in hard diskBoot process operating system kernel loaded into RAMKernel 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

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 commandsBootstrap program is built into special ROM chip in the computers system unit. When it receives power, it starts the boot processing by executing the bootstrap program.

Boot process major events
Power upStart boot programPower-on self-testIdentify peripheral devicesLoad operating systemCheck configuration and customization

OS in hard disks
Because RAM is volatile, we cant 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

6 major events during the boot process
Power upStart boot programpower-on self testIdentify peripheral devicesLoad OSCheck configuration and customization

Why OS is stored in HD not RAM
Because RAM is volatileEEPROM and ROM are non volatile but their storage capacity are not big enoughOS is transferred to RAM for quick access

Bootstrap summary

Microsoft Windows OS
Microsoft Windows (Windows 1.0, Windows 2.0Windows 2008)Adv: variety of hardware platforms, user community, gives excellent support in the form of built-in drivers and plug and play funcitonalityDisadv: reliability and securityThere are different Microsoft windows for different computer categories

Microsoft Windows versions

Personal computersLAN, Internet, and Web ServersPDAs, Mobile Phones, and Non-personal Computer DevicesWindows Vista Starter, Windows Vista Home Basic, Windows Vista Home PremiumWindows Server 2008Windows Server 2003Windows 2000 ServerWindows Mobile OSWindows Embedded OSWindows XP Embedded

MAC OS
Macintosh OSFor Apple Computers Macintosh line of computer systemsClassic 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 platformDisadv: limited selection of software

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

DOS (Disk Operating System)
First OS and old, developed by MicrosoftCommand-line user interface

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.

File Basics
File named collection of data that exists on a storage mediumFile-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

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.

File Directories and folders
You can choose a files locationDisk 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

Directory list of files for each storage diskRoot directory main directorySubdirectory smaller list subdivided from the root directorFolder File specification (Path) includes the drive letter, folder(s), file name, and extension.

File size measured in bytesOS keeps track of file sizes and supplies that information when you ask the list of the filesFile dateFile 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)

FILE FORMATS (OS and Executable Extensions)

Type of FileDescriptionExtensionBatch fileSequence of OS commands executed automatically when the comp boots.batConfiguration fileInfo about program the comp uses to distribute the resources needed to run them.cfg .sys .mif .bin .iniHelpThe info shown by on-screen Help.hlpTemporary fileA sort of scratch pad that has data while a file is open, but is discarded when you close the file.tmpSupport progProgram instructions executed along with the main .exe file for a prog.ocx .vbx .vbs .dllProgramMain executable files for a comp prog.exe .com

Data File Extensions

Type of fileExtensionsText.txt .dat .rtf .doc (Microsoft Word 2004) .docx (Word 2007).odt (OpenDocument text) .wpd (WordPerfect)Sound.wav .mid .mp3 .mp4 .aac .au .ra(Real Audio)Graphics.bmp .pcx .tif .wmf .gif .jpg .png .eps .ai(Adobe Illustrator)Animation/Video.flc .fli .avi .mpg .mov(QuickTime) .rm(RealMedia) .wmv(Windows Media Player)Web pages.htm .html .asp .vml .phpSpreadsheets.xls (Microsoft Excel 2003) .xlsx(Exel 2007) .ods(OpenDocument spreadsheet)Database .mdb (Microsoft Access) .odb(OpenOffice.org Base)Miscallenous.pdf (Adobe Acrobat) .ppt (Microsoft Powerpoint) .zip (WindZip) .pub (Microsoft Publisher) .qxp (QuarkXpress)

Why cant I open files
File damagedSomeone changed the file extensionSome file formats exist in several variations, and your software might have the capability to open a particular variation of the format.

Converting a file from one format to another
Easiest way to convert a fileOpen 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.

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

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

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

Save As option
Using apps, software interact with OSs file management system when youre opening and saving filesOS needs to know the name of a newly created fileApps checks with the OS to get list of available files (searching)

FILE MANAGEMENT UTILITIES
OS provide file management utilities that shows you the files stored on your disks and lets you work with themMac OS X FinderWindows 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.

FILE MANAGEMENT METAPHORS
Logical storage models metaphors that help you form a mental (logical) picture of the way in which files are storedFiling cabinetTree structureMicrosoft programmer combined the filing cabinet metaphor with the tree structure metaphor in the WINDOWS EXPLORER FILE MANAGEMENT UTILITY

Tree Structure

Windows Explorer

Physical File Storage
OS help you visualize computer storage as files and foldersPhysical storage model describes what really happens on the disks and in circuitsBefore storing, the storage medium must be formattedFormatting: process of dividing disk into tracks and sectors

Tracks and Sectors

OS keeping track of a files location
OS uses file system. Different systems use different file systemsMac 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

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 variesA file system primary task is to maintain a list of clusters and keep track of which are empty and which hold data.

This information is stored in a special index fileFAT32 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.

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 clusterIf the file is too big to fit in one cluster, it will use more clusters that are next to it

MFT keeps track of file names and locations

Opening a file
When you open a file,The OS looks up the filename in the Master File Table.It finds the correct cluster and sector on the hard driveThen it moves the read-write head on the hard disk to that spot. The read-write head will read that dataThe data is sent back to the RAM for the OS to use

Deleting a file
If you want to delete a file, you might think that it is erased from the hard diskInstead the master file table is updated to say that cluster is now empty and can be used for new dataThere are programs that allow users to recover deleted items, because THEY ARE NOT REALLY DELETEDTo really delete a file, you can use special file shredder software, that overwrites supposedly empty sectors with random 1s and 0s.

Can deleted files be undeleted?
The Windows Recycle Bin and similar utilities in other OS are designed to protect you from accidentally deleting hard disk files you actually needFiles in the Recycle Bin Folder can be undeleted so that they again appear in the regular directory.The Recycle Bin can be emptied to permanently delete any files it contains.

Fragmentation
As computer writes files on a disk, parts of files tend to become scattered all over the disk and stored in noncontiguous clusters which refer to Fragmented files. Drive performance generally declines as the read-write heads move back and fourth to locate the clusters containing the parts of a file.

Defragmentation

Data Backup
It is often important to save your data in two places, in case one place goes bad. Maybe your hard disk will break, your file system will break or your CD-ROM will get scratchedIf you have important data, save it in another place, because you never know what will happen

Data Backup
You can make a backup of your entire computer (called full backup), but often its not worth it. You can always re-install the operating system and get the applications you had beforeThe things you cannot replace are documents and files that you create. Those should be saved.

FILE COPIES AND SYNCHRONIZATION
File synchronization software: automatically make copies of files in specified folders. Ensures files in two or more locations contain the same data (E.g. Time Machine with Mac OS X)

File and system software
Backup softwareFull backup: makes a fresh copy of every file in the folders youve specified for backupDifferential backup: makes a backup of only those files that were added or changed since your last full backup sessionIncremental backup: makes a backup of the files that were added or changed since the last backup

Window software are designed to run on computers that have Microsoft Windows (MSWord, Excel etc.) Mac Software is designed to run under Mac OS. Linux software is designed to run under Linux operating system
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You issue print while using app software (Word) Word processing app signals OS that document must be sent to the printer OS communicates the doc data to the device driver for printer device driver controls printer as it prints the document
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The operating system interacts with application software, device drivers, and hardware to manage a computers resources. In the context of a computer system, the term resource refers to any component that is required to do work. E.g. processor is a resource. RAM, storage space, and peripherals are also resources.
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Multitasking provides process and memory management services that allow two or more tasks, jobs, or programs to run simultaneously. Most of todays operating systems offer multitasking.Within a single program, multithreading allows multiple parts, or threads to run simultaneously. E.g. one thread for a spreadsheet program might be waiting for input from the user while other threads perform a long calculation in the background. Multithreading can speed up a performance on single or multiple processor computers.Many new computers include multi-core processors or multiple processors. An OS multiprocessing capability supports a division of labour among all the processing units.
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Filing clerk that stores and retrieves files from your disks or CDs
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Keyboard buffer you never miss a stroke no matter how fast you type
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OS defines the look and feel of compatible softwareGraphical user interface (GUI): point and click.Icon small picture that represents a program, file, or hardwareWindow rectangular work area that hold a program, data, or controls
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1. Power light is on, power distributed to the comp circuitry. 2. microprocessor starts executing bootstrap prog stored in ROM. 3. comp does diagnostic test of several very important system parts. 4. OS identifies peripherals and their settings. 5. OS copied from HD to RAM. 6. microprocessor reads config data and does any specially made startup techniques specified by the user.
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Different platforms desktop, notebook, ultr-mobile PC, tablet computer, handwriting recognition for PDAs and tablet comps with touch screensUser community vast amount of documentation, including tutorials and troubleshooting guidesMany of the fastest graphic cards are offered exclusively for the Windows platformDisad: compared to other OS in speed
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Backward compatibility ability to work with products designed for prior-generation hardware and software. E.g. suppose you have a computer and lots of great software, but you purchase a faster machine with an upgraded OS. If the OS is backward compatibility with the OS on your old computer, you can use all of your old applications.Dual boot can switch between Mac OS X and Windows. When booting, you can select either Mac OS X or Windows. To change operating systems, you have to reboot.Virtual machine technology that allow you to use one computer to copy the hardware and software of another
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UNIX available for mainframes and microcomputersLinux is designed for microcomputers rather than mainframes.
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File specification e.g. C:\Music\Reggae\Marley One Love.mp3
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File format - E.g. graphics data can be stored in file formats such as bitmap, GIF, JPEG, or PNG.
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File Extension is NOT the same as file format extension is a good indicator of a files format
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File damaged corrupt by a transmission or disk error. You can use file recovery to repairFile extension changed if a file contains a graphic, open with apps that do so
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Defragmentation: a defragmenter rearrange the files on a disk so that they are stored in contiguous (adjacent or nearby) clusters.
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tonga institute of higher education it 141

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