OPERATING SYSTEM<br />OPERATING SYSTEM: is system software that works as an interface between a user and the computer hardware.<br />PRIMARY OBJECTIVES:<br /><ul><li>To make computer system convenient to use.
To utilize computer hardware in an efficient manner.</li></ul>EXAMPLE: UNIX, MS-DOS, MS-Windows, Windows NT/2000,OS/2 and Mac OS.<br />MAIN JOBS OF OS:<br /><ul><li>RESOURCE MANAGER: manages hardware software resources of the computer system and resources include processor, memory, disk space etc.
APPICATION CONTROLLER: provides stable, consistent way for applications to deal with hardware without knowing of its detail.
</li></ul>PROCESSOR MANAGEMENT AND SCHEDULING: <br /><ul><li>OS manages various peripherals and resources of computer, user’s request, instructions and commands, and schedules the job for CPU to carry out in sequence.
It handles interrupt requirements and reschedules it accordingly.</li></ul>DEVICE MANAGEMENT<br /><ul><li>OS monitors the availability and working conditions or status of these devices, as shareable (discs, tapes, main memory) or non-shareable (printer monitor, keyboard)
It takes care of illegal instructions or commands, reports error accordingly.
It also manages BIOS (Basic Input Output Control System). </li></ul>FILE AND DATA MANAGEMENT<br /><ul><li>It sets up directories and stores user files, blocks and stores record.
It transfers main memory contents in specific filenames, to discs and vice versa.
It displays the name of files stored, their sizes, and request permissions for overwriting or erasing and warning such as space not available etc.</li></ul>SECURITY<br /><ul><li>A computer system may contain highly private data and OS ensures that the security is maintained by protecting against destruction and unauthorized access.</li></ul>COMMAND INTERPRETATION AND EXECUTION<br /><ul><li>OS reads the commands entered by users, checks for errors, interprets and then into machine instructions and gets them executed by the hardware.</li></ul>FAULT TOLERANCE<br /><ul><li>It is built-in with OS, providing replication and dual hard disks.
In any interface or peripheral device failure, system automatically switches over to substitutes, and keeps processor on.</li></ul>MEMORY MANAGEMENT<br /><ul><li>It provides available memory for processing, such as accepting the keyboard & storing results or outputs.
OS partitions memory for different users and programs.
In multiuser, memory allocation is dynamic.</li></ul>JO B ACCOUNTING<br /><ul><li>OS, with the help of an internal time clock computes the time each resources (peripherals and CPU) is used by different users.
It also maintains a log and keeps track of login and logout of particular users, commands entered by user, files used, and jobs carried out.