Process Creation


  • Parent process create children processes, which, in turn create other processes, forming a tree of processes
  • Generally, process identified and managed via a process identifier (pid)
  • 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


  • Process Creation




    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 systems do not allow child to continue if its parent terminates
        • All children terminated - cascading terminati




  • Quantitative Aptitude
    Reasoning
    Programming
    Interview