An operating system is a set of programs that lies between applications software and the computer hardware. Conceptually the operating system software is an intermediary between the hardware and the applications software. The operating system is the core software component of your computer. It performs many functions on an interface between your computer and the outside world.
There are many functions of operating system :-
1. The platform to work properly with high resource utilization and in a very fast mode. System tools (programs) used to monitor computer performance or maintain parts of the system.
2. A set of libraries or functions which programs may use to perform specific tasks especially relating to interfacing with computer system components.
3. Manage the computer resources, such as the central processing unit, memory, disk drives, and printers.
4. Establish a user interface.The operating system makes these interfacing functions along with its other functions operate smoothly and these functions are mostly transparent to the user.
5.Execute and provide services for applications software. Input/output management, that is, co-ordination and assignment of the different output and input device while one or more programs are being executed.
6. Processor management that is assignment of processor to different tasks being performed by the computer system.
7. Memory management that is allocation of main memory and other storage areas to the system programs as well as user programmers and data.
8. File management that is the storage of file of various storage devices to another. It also allows all files to be easily changed and modified through the use of text editors or some other files manipulation routines.
9. Establishment and enforcement of a priority system. That is, it determines and maintains the order in which jobs are to be executed in the computer system.
10. Automatic transition from job to job as directed by special control statements.
11. Coordination and assignment of compilers, assemblers, utility programs, and other software to the various user of the computer system.
12. Facilities easy communication between the computer system and the computer operator (human). It also establishes data security and integrity.
13. To give the user a GUI (graphical user interface) basically it means that instead of using dos commands to move from folder to folder they have a program that will let them see an icon of the folder so they can click on it.
14. Time-sharing system
~ With multiprogramming, the overall system is quite efficient. However a problem remains. That is those jobs that come late in the batch job list won’t get chance to run until the jobs before them have completed, thus their users have to wait a long time to obtain the results. Some programs may even need interaction with users, which requires the processor to switch to these programs frequently. In such a system, multiple users simultaneously access the system through terminals, with the operating system interleaving the execution of each user program in a short burst of computation.
15. The operating system is also in charge of traffic controller or manage the data that is coming into the computer (input by way of the keyboard or mouse) and going out of the computer (output by way of printer or screen display). It directs the flow of data to and from the external devices and also takes care of control routing information along the bus to be processed by the processor.
16. The operating system also is the maintenance mechanic of the system. It checks the system for failures that will cause problems in processing. Messages will appear on the screen when there is a problem. Sometimes operating systems will have built in messages for quick fixes to the problem, or will refer you to a resource to get more information. A typical message that one would see is "System Failure" or "Your computer has performed an illegal operation". When the computer is turned on, the computer checks all of the storage devices. You can see the system being checked by the lights going off and on at the various drive locations. All of the electronic parts are checked also. If the computer can not do a self fix, it will not let you continue working.
17. Control to the computer hardware . The operating system sits between the programs and the Basic Input Output System (BIOS). The BIOS controls the hardware. All programs that need hardware resources must go through the operating system. The operating system can either access the hardware through the BIOS or through the device drivers.
18. Support for built-in utility programs .The operating system uses utility programs for maintenance and repairs. Utility programs help identify problems, locate lost files, repair damaged files, and backup data. The figure here shows the progress of the Disk Defragmenter, which is found in Programs > Accessories > System Tools.
19. Running applications .These programs load and run applications such as word processors and spreadsheets. When a user requests a program, the operating system locates the application and loads it into the primary memory or RAM of the computer. As more programs are loaded, the operating system must allocate the computer resources.
20. Provides network capability. Each user has a single processor but can share data and resources with other users connected to the network. The OS must be able to detect if more than one user is trying to send messages at the same time. Networks may make use of spooling techniques to share peripherals such as printers. Networks may be Local Area or Wide Area, LAN or WAN. A LAN is wired together within the same site and can take a number of different forms, (topologies), Bus, Star, Ring. One machine on the network often acts as a file server looking after a high capacity storage device. WANS are computers linked via gateways to other computers which are geographically distant. They may make use of dedicated phone lines or go through the normal BT lines using modems. They usually use packet switching techniques to transfer data between nodes.
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