(1) Introduction To Os

Operating Systems: Software in the Background Wednesday, July 02, 2008

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Softwares

System Software

• Computer Program or Program

• System Software –Operates the computer. –Controls the hardware. –Interface between user, application software and hardware.

• 2 Types of Software –Application Software –System Software

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System Software (cont.)

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System Software (cont.) • Operating Systems

• 2 Types of System Software

–Coordinates the hardware devices. –Enables running of application softwares.

–Operating System –Utility Programs

• Software platform –Cross-platform applications Wednesday, July 02, 2008

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System Software (cont.)

Operating System Objectives • Determines how valuable RAM is allotted to programs • Performs tasks related to file management • Sets priorities for handling tasks • Manages the flow of instructions, data, and information to and from the processor

• Utility Programs –Computer management functions.

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Operating System Functions • • • • • • •

Operating System Functions (cont.)

Staring a Computer The User Interface Managing Programs Managing Memory Scheduling Jobs Configuring Devices Accessing the Web

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• Accessing the Web • Monitoring Performance • Providing Housekeeping Services • Controlling a Network • Administering Security 9

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Starting a Computer (cont.)

Staring a Computer

• When you boot, the kernel

• Booting

and other frequently used operating system instructions are loaded from the hard disk to the memory.

–Process of staring or restarting the computer.

• 2 Types of Booting –Cold Boot –Warm Boot Wednesday, July 02, 2008

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Starting a Computer (cont.) • Kernel

Starting a Computer (cont.) 1. The power supply sends a signal to the components in the system unit. 2. The processor finds the ROM chip(s) that contain the BIOS.

–Core of OS –Manages memory and devices • Maintains the computer’s clock • Starts applications • Assigns computer resources

–Memory-resident Wednesday, July 02, 2008

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Starting a Computer (cont.) BIOS-basic input/output system, contains the startup instructions.

3. The BIOS performs the POST. POST-power-on self test, checks system components,LEDs flicker,beeps sounds, messages are displayed.

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Starting a Computer (cont.) 4. The results of the POST are compared with data in the CMOS chip. CMOS chip-stores configuration info about the computer.

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Starting a Computer (cont.) 5. The BIOS looks for the system files. 6. The system files and the kernel of the operating system load into memory from storage.

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Starting a Computer (cont.) 7. The operating system loads configuration information and displays the desktop on the screen. Startup Folder-contains programs that open automatically when the computer boots.

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Starting a Computer (cont.) • Boot Drive

The User Interface • User Interface

–Drive where computer boots.

–Controls data entry and instructions. –Display

• Recovery Disk –Emergency repair disk, boot disk, rescue disk.

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The User Interface (cont.)

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The User Interface (cont.)

• Text-Based Software

• MS-DOS (Microsoft Disk Operating System)

–Enter or “type” commands through a keyboard.

• Ex: c:\>copy c:\file.doc to a: • Command-line interface –Command language Wednesday, July 02, 2008

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The User Interface (cont.)

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Allocating System Resources

• Graphical User Interface

• Single user/single tasking

–Interact using visual images –Select commands by “pointing and clicking” with a mouse.

• Multiuser

• Icon – represents a program, instruction, or some file.

–Select commands by “pointing and clicking” with a mouse. Wednesday, July 02, 2008

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Allocating System Resources (cont.)

Allocating System Resources (cont.)

• Multitasking

• Multithreading

–(Virtually) Concurrent execution of program. –Possible through difference in speed peripheral devices.

–(Real-time) Concurrent execution of program

• Multiprocessing –Fault-tolerant computers

–Foreground • Lion’s share

–Background Wednesday, July 02, 2008

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Managing Memory (cont.)

Managing Memory

–Page – amount of data and programs instructions that can swap at a given time.

• Memory Management –Optimize use of RAM

• Virtual Memory

–Paging – technique of swapping items between memory of storage.

–Portion of storage to function as memory (Swap File)

–Thrashing Wednesday, July 02, 2008

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Scheduling Jobs (cont.)

Scheduling Jobs • Job

• Spooling

–Operation managed by the processor.

–Common for print jobs. –Sends print jobs to a buffer, rather than immediately to the printer.

• Buffer –Segment of memory or storage in which items are placed while waiting to be processed. Wednesday, July 02, 2008

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–Queue – method in spooling 29

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Configuring Devices (cont.)

Configuring Devices • Device Driver

• IRQ

–Tells the OS how to communicate to a device.

–Interrupt request –Communication line between the device and processor.

• Plug and Play –Automatically installs drivers. Wednesday, July 02, 2008

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Monitoring Performance

Accessing the Web • Web browser

• Performance Monitor

–Browsing –Chatting –E-mailing

–Assesses and reports information about various system resources and devices. –Task Manager

• On-Line

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Providing Housekeeping Services

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Providing Housekeeping Services (cont.) • Organizing, copying, renaming,

• File Manager

–Performs functions related to storage and file management. • Formatting or copying disks • Displaying files • Checking used or free space

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deleting, moving, and sorting files; creating shortcuts. Shortcuts – are icons on the desktop that runs a program when you click it.

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Providing Housekeeping Services (cont.)

Controlling a Network

• Formatting

• Network Operating System

–Process of preparing a disk for reading and writing.

–Operating system that supports a network.

• File Allocation Table (FAT) –Table of information that the OS uses to locate files on a disk. Wednesday, July 02, 2008

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• Server – controls access to the HW and SW on the network. • Clients – other computers on a network.

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Administering Security

Administering Security (cont.)

• Log-on

• Passwords – Combination of characters associated with the username that allows access to computer resources.

• Usernames –Unique combination of characters that identifies one specific user.

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• Asterisks (*)

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Types of Operating Systems 1. Stand-Alone Operating Systems 2. Network Operating Systems 3. Embedded Operating Systems

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Stand-alone OS • Works on desktops and notebooks • Also called client

operating systems.

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Stand-alone OS (cont.) • • • • • •

DOS Windows Windows Windows Windows Windows

Stand-alone OS (cont.) • Windows XP • MAC OS • OS/2 Warp Client

3.x NT Workstation 98 2000 Professional Millennium Edition

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Network OS

Network OS (cont.)

• Supports a network • Typically resides on a server.

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• • • • •

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Netware Windows NT Server Windows 2000 Server Windows .Net Server OS/2 Warp Server for EBusiness

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Network OS (cont.)

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Embedded OS

• Unix • Linux • Solaris

• Operating systems on most handheld devices. • Resides on the ROM chip.

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Embedded OS (cont.)

Utility Programs • Referred to as utilities. • Performs tasks related to managing the computer, devices, or programs.

• Windows CE • Pocket PC 2002 • Palm OS

• Utility Programs – several utility programs in one package. Wednesday, July 02, 2008

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Functions of Utility Programs • • • • • • • •

File Viewer

Viewing Files Compressing Files Diagnosing Problems Uninstalling Software Scanning Disks Defragmenting Disks Backing up Files and Disks Displaying Screen Savers

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• Allows you to display and copy contents of a file • Picture and Fax Viewer

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File Compression

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Diagnostic Utility

• Shrinks the size of a file. • Helps free up room on storage media.

• Compiles technical information and prepares reports for identified problems.

• Zipped Files -> .zip / .rar

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Uninstaller

Disk Scanner

• Removes installed applications.

• Detects and corrects both physical and logical problems on disk.

• Removes associated files in system.

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• Searches for and removes unnecessary files.

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Disk Scanner (cont.)

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Disk Defragmenter

• Physical Problem

• Reorganizes the files and unused space on disks, which allows faster access to data.

–One with the media such as scratches on disk surface.

• Logical Problem –Problem with data such as corruption or cyclic redundancy checks. Wednesday, July 02, 2008

• Arranges files in contiguous sectors. 57

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Disk Defragmenter (cont.)

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Backup Utility

• When the contents of a file

• Allows you to copy, or backup, selected files or entire disk onto another.

are scattered across two or more noncontiguous sectors, the file is Fragmented.

• During backup, it monitors

progress and alerts if additional space.

• Fragmentation slows down disk access. Wednesday, July 02, 2008

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Backup Utility (cont.)

Screen Saver

• Some backup programs, compress files.

• Causes a monitor’s screen to display multimedia or a blank screen during idle time.

• Restore Program –Returns backed up files to their original form.

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• Originally invented to prevent ghosting. 61

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Screen Savers (cont.) • Ghosting –Problem with monitors during the old days. –Permanently etched images on a monitor’s screen.

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