Process control block

 What is process control block (PCB)?

              When a user initiates of a  new process, the OS collect all the information that is need about that particular process into a data structure called as a process control block (PCB) or task control block.

             It act repository for any information for process. PCB is implemented as a record containing vital information like process state scheduling information, access control information etc. Show in the following figure------

Fig: process control block

 What is parent process and child process?

            The process creating a new process is called parent process.

            If a process p1 can create another process p2, then p2 is called child process of parent process p1.

What is context switch?

            

               It is a typical of interrupt handler. Context means the state, i.e., state of the process. Switching means switch from one process to another process.

                When an interrupt occur, the primary work is does, is to save the context of the current process. Saving a process is called half context switch. The other half of the context switch is the restoring of the context of the next process to run. The saving and restoring is called a full context switch.