COMPUTER FUNDAMENTALS David Samuel Bhatti

Operating System

Systems Software  System software…  Increases the performance of the computer systems  Examples Operating Systems Language Compilers Utility Programs Operating Systems An operating system is an interface between the hardware of a computer and the user (program or human) that facilitates the execution of the other programs and the access to hardware and software resources

Operating System Functions  Running Programs  Device Management  File Management  Providing a user interface (graphical or not) to system functions and resources  Hardware Independence  User authentication  Processor allocation (process scheduling)  Process synchronization  Interprocess communication  Memory Management  Network Management

Running Programs  Many different applications supported  System call  Provides consistent access to OS features  Share information between programs  Copy and paste  Object Linking and Embedding

Device Management  Programs need to access hardware  Interrupts  CPU is stopped  Hardware device is accessed  Device drivers control the hardware

File Management  Organized storage  Long file names  Folders can be created and nested  All storage devices work consistently

Providing Interface  User interface A function of the operating system that allows individuals to access and command the computer  Command-based user interface A particular user interface that requires text commands be given to the computer to perform basic activities E.g., unix, DOS  Graphical user interface (GUI) A user interface that uses pictures (icons) and menus displayed on the screen to send commands to the computer system E.g. Windows, MAC OS

Hardware Independence  Operating system (OS) provides hardware independence for application software  Application software interfaces with the operating system which interfaces with the hardware  When the hardware is changed, the operating system is changed so that the application software is not required to be changed Users Application software Operating and systems software Hardwar e

Authentication

Process Management Special thanks to Dr P. K. Sinah for using slides

Operating System Concepts  Multitasking  A processing activity that allows a user to run more than one application at the same time  Multithreading  A processing activity that is basically multitasking within a single application  Time-sharing  A processing activity that allows more than one person to use a computer system at the same time

Types of Operating Systems(I)  Real-time operating system  Very fast small OS  Built into a device  Respond quickly to user input  MP3 players, Medical devices  Single User OS  Used as desktop  Single user  Do not have the networking capabilities  e.g DOS, Windows 3.x  Multi User OS  Have capabilities to create a network

Types of Operating System(II)  Single Tasking  Operating System cannot be able to take control back from the running process/task/application  In case if a process call an I/O Instruction then Processor must wait for I/O instruction to complete before preceding

Types of Operating System(III)  Multitasking  Operating System can take control back from the running process and can give it to other.  When one job needs to wait for I/O, the processor can switch to the other job

Operating System Objectives  Convenience  Makes the computer more convenient to use  Efficiency  Allows computer system resources to be used in an efficient manner  Ability to evolve  Permit effective development, testing, and introduction of new system functions without interfering with service

Layers of Computer System

Services Provided by the Operating System  Program development  Editors and debuggers  Program execution  Access to I/O devices  Controlled access to files  System access

Enhancing an OS(I)  Utilities  Provide services not included with OS  Goes beyond the four functions  Firewall, anti-virus and compression  Prices vary

Enhancing an OS(II)  Backup software  Archives files onto removable media  Ensures data integrity  Most OS include a backup package  Many third party packages exist

Backup Software(III)

Enhancing an OS(IV)  Anti-virus software  Crucial utility  Finds, blocks and removes viruses  Must be updated regularly  McAfee and Norton Anti-Virus

Enhancing an OS(V)  Firewall  Crucial utility  Protects your computer from intruders  Makes computer invisible to hackers  Zone Alarm for windows

Enhancing an OS(VI)  Intrusion detection  Often part of a firewall package  Announces attempts to breach security  Snort is a Linux based package

Enhancing an OS(VII)  Screen savers  Crucial utility for command line systems Prevents burn in  Merely fun for GUI systems  Screen saver decorates idle screens