Friday, October 7, 2016

                                      Operating System 

The operating system is the most important program that runs on a computer. It is the software that supports a computer's basic functions such as scheduling tasks, executing applications, and controlling peripherals. Every general purpose computer must have an operating system to run other programs and applications. For large  systems, the operating system has even greater responsibilities and powers. It makes sure that different programs and users running at the same time do not interfere with each other.


 What is the classification of Operating Systems?

 TheOperating System can be of different types :
  • Multi-user: It allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.
  • Multi-tasking : It supports running a program on more than one CPU.
  • Multi-processing: It allows more than one program to run concurrently.
  • Multi-threading: It allows different parts of a single program to run concurrently.
  • Real Time: It responds to input instantly.The general-purpose operating systems are not real time. 

What are the functions of operating systems ?

  • Memory Management: Memory management refers to the management of Primary Memory or Main Memory. Main Memory is a large array of words or bytes where each word or byte has its own address.The operating system does the following activities:
            - Keeps track of primary memory
            - In Multiprogramming, the OS decides which process will get me memory and how much
            - allocates the memory when a process requests it to do so.
            - De-allocates the memory when a process no longer needs it or has been terminated.
  • Processor Management:In multiprogramming environment, the OS decides which process gets the processor when and for how much time. This function is called Process Scheduling. An Operating System does the following activities for Processor management:   
          -Keeps track of processor and status of the process. The program responsible for this task is                  known as Traffic Controller
          -Allocate a processor(CPU) to a process
          - De-Allocate processor when a process is no longer required
  • Device Management:An operating System manages device communication via their respective drivers. The Operating System does the following Activities for the Device Management -
           - Keeps track of all devices.Program responsible for this task is known as I/O Controller
           - Decides which process gets the device when and for how much time.
           - Allocates the device in the efficient way.
           - De-allocates devices.
  • File Management: A file system is normally organized into directories for easy navigation and usage. These directories may contain files and other directions.An operating System does the following activities for file management:
           - Keeps track of information, location, uses, status and etc. The collective facilities are often                  known as file system.
           - Decides who gets the resources.
           - Allocates the resources.
           - De-allocate the resources.
  • Others : The other important Activities include:
            - Security
            - Control over system performances
            - Job accounting 
            - Error detecting aids
            - Coordination between other softwares and users.

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References

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