Process Creation

Parent process creates child processes, which, in turn create other processes, forming a tree of processes. It is called process creation.

 Resource sharing:

✦ Parent and child share all resources.

✦ Children share the subset of parent’s resources.

✦ Parent and child share no resources.

Execution:

✦In the Operating System, the Parent process and child process execute simultaneously.

✦ Parent waits until child terminates.

Address space:  

✦ Child duplicate of the parent.

✦ The child has a program loaded into it.

UNIX examples

✦ fork system call creates a new process.

✦ exec system call used after a fork to replace the process’ memory space with a new program.

Process Termination

• The process executes the last statement and asks the operating system to decide it (exit).

✦ Output data from child to parent (via wait).

✦ Process’ resources are deallocated by an operating system.

• A parent may terminate execution of children processes (abort).

✦ The child has exceeded allocated resources.

✦ The task assigned to the child is no longer required.

✦ Parent is existing.

✔ An operating system does not allow the child to continue if its parent terminates.

✔ Cascading termination.