Operations on Processes

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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

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