Define the following (i) Process; (ii) Process Control Block; (PCB) (iii) Multi programming; (iv)Time sharing.

Ans:

      (i) Process:  

        Process is a program in execution; process execution must progress in sequential fashion. A process     includes:

• program counter
  
• stack
  
• data section 
  

  (ii) Process Control Block (PCB):  

  
  Information associated with each process is stored in Process control Block.
  Process state
  Program counter
  CPU registers
  CPU scheduling information
  Memory-management information
  Accounting information
  I/O status information
  

  (iii) Multiprogramming: 

  
   A multiprogramming operating system is system that allows more than one active user program (or part of user program) to be stored in main memory simultaneously. Multi programmed operating systems are fairly sophisticated. All the jobs that enter the system are kept in the job pool. This pool consists of all processes residing on mass storage awaiting allocation of main memory. If several jobs are ready to be brought into memory, and there is not enough room for all of them, then the system must choose among them. A time-sharing system is a multiprogramming system.
  

  (iv) Time Sharing:

  
   Sharing of a computing resource among many users by means of multiprogramming and multi-tasking is known as timesharing. By allowing a large number of users to interact concurrently with a single computer, time-sharing dramatically lowered the cost of providing computing capability, made it possible for individuals and organizations to use a computer without owning one, and promoted the interactive use of computers and the development of new interactive applications.