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
• 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

Process Creation

b.) 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
  - Task assigned to child is no longer required
  - If parent is exiting
  - Some operating system do not allow child to continue if its parent terminates
  –All children terminated - cascading termination