UNIX processes are '''hierarchical''':This * The process structure has a '''root''', '''parents''', and '''children'''* Creation of a new process is called '''forking ''' or '''spawning'''* Each process has its own '''PID''' (''process ID number'')* The Parent process can fork spawn a child and children can fork spawn their own children* Processes keep their '''PID ''' for their entire life* Usually a parent sleeps when a child is executing– The (the exception is when the child process is executing in the background)