operating system
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What is an Operating System?What is an Operating System?What is an Operating System?What is an Operating System?
The operating system is the most importantprogram that runs on a computer. Every general-purpose computer must have an operating systemto run other programs. Operating systems performto run other programs. Operating systems performbasic tasks, such as recognizing input from thekeyboard, sending output to the display screen,keeping track of files and directories on the disk,and controlling peripheral devices such as diskdrives and printers.
What is an Operating System?.....What is an Operating System?.....What is an Operating System?.....What is an Operating System?.....Cont’dCont’dCont’dCont’d
For large systems, the operating system has evengreater responsibilities and powers. It is like atraffic cop -- it makes sure that different programsand users running at the same time do not interfereand users running at the same time do not interferewith each other. The operating system is alsoresponsible for security, ensuring that unauthorizedusers do not access the system.
Tasks Carried out by Operating SystemTasks Carried out by Operating SystemTasks Carried out by Operating SystemTasks Carried out by Operating System
� Input/output/peripheral/device control� File (copy/save/delete etc) Management� User interface� Load/run software� Memory Management� Memory Management� Error Handling� Security Management� Multiprogramming� Processor Management� Power Management
Command Line InterfaceCommand Line InterfaceCommand Line InterfaceCommand Line Interface
CLI Short for command line interface, a userinterface common to MS-DOS computers. The usersees the command line on the monitor and aprompt that is waiting to accept instructions fromprompt that is waiting to accept instructions fromthe user. The user types in the command, thecomputer acts on that command and then issues anew prompt for the next instruction from the user.
Command Line Interface….. Command Line Interface….. Command Line Interface….. Command Line Interface….. Cont’dCont’dCont’dCont’d
Command Line InterfaceCommand Line InterfaceCommand Line InterfaceCommand Line Interface
Advantages of CLI :� direct communication with computer system� not restricted to a number of pre-determined options� simple interface using keyboard onlyfaster response� faster response
Disadvantage of CLI:� need to learn a number of/long/complex commands� need to type in the commands (possibility of errors)� slow having to type in commands every time
Graphical User InterfaceGraphical User InterfaceGraphical User InterfaceGraphical User Interface
Graphical User Interface AbbreviatedGUI (pronounced GOO-ee). A programinterface that takes advantage of thecomputer's graphics capabilities to make thecomputer's graphics capabilities to make theprogram easier to use. Well-designedgraphical user interfaces can free the userfrom learning complex command languages.
Graphical User Interface…… Graphical User Interface…… Graphical User Interface…… Graphical User Interface…… Cont’dCont’dCont’dCont’d
Graphical user interfaces, feature the following basic components:
� Pointer :A symbol that appears on the display screen and that you move to selectobjects and commands. Usually, the pointer appears as a small angled arrow.
� Pointing Device :A device, such as a mouse or trackball, that enables you to select objects on the display screen.
� Icons : Small pictures that represent commands, files, or windows. By moving the � Icons : Small pictures that represent commands, files, or windows. By moving the pointer to the icon and pressing a mouse button, you can execute a command or convert the icon into a window. You can also move the icons around the display screen as if they were real objects on your desk.
� Desktop :The area on the display screen where icons are grouped is often referred to as the desktop because the icons are intended to represent real objects on a real desktop.
� Windows:You can divide the screen into different areas. In each window, you can run a different program or display a different file. You can move windows around the display screen, and change their shape and size at will.
� Menus :Most graphical user interfaces let you execute commands by selecting a choice from a menu.
Graphical User Interface…… Graphical User Interface…… Graphical User Interface…… Graphical User Interface…… Cont’dCont’dCont’dCont’d
Graphical User InterfaceGraphical User InterfaceGraphical User InterfaceGraphical User Interface
Advantages of GUI :� only need to click on one simple picture� so much easier for the novice� several instructions are replaced by one icon� no need to understand how computer systems work� no need to understand how computer systems work
Disadvantage of GUI:� wasteful of computer memory� if user wants to communicate with computer system directly, GUI is effectively more complex.
