Operating system 4

3.Operations on Processes

A-Process Creation
-Parent process create 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.
Process creation(cont.)
-Address space
-Child duplicate of parent.
-Child has a program loaded into it.
-UNIX examples
-fork system call creates new process
-exec system call used after a fork to replace the process’ memory space with a new program.

B-Process Termination

-Process executes last statement and asks the operating system to decide 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.
-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.