OPERATION'S ON PROCESSESS

PROCESS CREATION
:Parent process creates children processes, which, in turn create other processes, forming a tree of processes.
:Resource sharing
> Parent and children share all resources.
> Children share subset of parent’s resources.
> Parent and child share no resources.
: Execution
>Parent and children execute concurrently.
> Parent waits until children terminate.
:Address space
> Child duplicate of parent.
> Child has a program loaded into it.
: UNIX examples
> fork system call creates new process
> fork returns 0 to child , process id of child for parent
> exec system call used after a fork to replace the process’ memory space with a new program.

PROCESS TERMINATION

:Process executes last statement and asks the operating system to delete it (exit).
>Output data from child to parent (via wait).
> Process’ resources are deallocated by operating system.
: Parent may terminate execution of children processes (abort).
> Child has exceeded allocated resources.F
>Task assigned to child is no longer required.
> Parent is exiting.
>>Operating system does not allow child to continue if its parent terminates.
>> Cascading termination.
: In Unix, if parent exits children are assigned init as parent