What is operating system?

    An integrated set of program, which control the resources of a computer system and provides its user with an interface or virtual machine,which is more convenient to use then the bore machine.
   
      The operating system acts as the manager of resources and allocates them to specific program and user as necessary for there task. Therefore operating system is the resource management that is it can manage the resource of a computer system internally.

       The operating system also a virtual computer manager that provides virtual computer for process to runing.


 Goal of os:
        1.The primary goal of the os is to make the computer system convenient to use (handy,suitably i.e easy to use).
       
        2.The secondary goal of the os is to use the computer hardware in an efficient manner.
   
  Os may be characterized by---------
              
             a) Batch os
             b) Multiprogramming os
             c) Time sharing os
             d) Real time os
             e) Network os
             f) Distributed os
        

a) Batch os:
                         Batch os allow a continuous series of job is to be loaded automatically from an input device. To identify the various job and its function a special language is use-- known as JCL on Job Control Language. scheduling of job may be FCFS or SJN. In this system at most one program is execution at any time,so no time devision management is required. 
          Batch processing have a better scope for resources utilisation due to it serial process. As a result the program like statistical analysis,seientific program etc, that require long execution time and no interaction with other,is suitable in batch os.

 b) Multiprogramming  os:
                                                     This is the fast os where the os make decision for the user. In this system, the design of autonomous Peripheral device which can carry out input output operations independently while the CPU continuous to execute program.

  c)  Time sharing os:
                                         In this system,the CPU is allocated to each user in term for a small time slice. As soon as the time slice is over, the CPU switches to the next user.

  d)  Real time os:
                                  A real time system is a system when it is interacting with a real-world process that will move at a certain rate. 
       The primary objective of real time OS is to provide quick-even response time and thus meet the scheduling deadline. 

   e) Network os:
                                 A network os is defined as a collection of software and associated protocols that allows a set of autonomous computers, which are interconnected by a computer network to be used together in a convenient and cost effective manner.

   f) Distributed os:
                                    A distributed OS hide the existence of multiple computer and provide a single system image to the user. So, a user of a distributed operating system knowledge of the machine on which job execute.