<<<<<< TIME POSE SUBROUTINE >>>>>>>>>

PAUSE

If they want to quit, do so

    <<<<<< 4 BOTTOM LINES CLEANING SUBROUTINE >>>>>>

BOTCLEAN

If they want to quit, do so

ENCORE5

    <<<<<< REVIEW CLEANING SUBROUTINE >>>>>>

CLEAN

If they want to quit, do so

ENCORE

    <<<<<< CLEAN THE INSIDE OF BOUNDED ARE ONLY >>>>>

BOX

                       ILLUSTRATION                     

GO

 A process is an instance of a program in execution.

 Assume that Process 1 is a program called A,

           Program A

 Process 1  -------->

 When program A issues a fork(), a parent and a child process are created.

           Program A fork()

 Process 1  -------->  V -------->

                       | parent

                       |

                       |

                       | Program A

 Process 2             -------------

                         child

 Normally, the parent process issues a wait() ...

           Program A  fork        wait

 Process 1  -------->  V -------->||

                       | parent

                       |

                       |

                       | Program A

 Process 2             -------------

                         child

 ... and the child issues an exec of a new program, B:

           Program A  fork        wait

 Process 1  -------->  V -------->||

                       | parent

                       |

                       |

                       | Program A

 Process 2             -------------[ exec B]

                         child

 At this point, the parent of program A is asleep and B is running.

           Program A  fork        wait

 Process 1  -------->  V -------->||- : - : - : - : - : -

                       | parent          (sleeping)

                       |

                       |

                       | Program A             Program B

 Process 2             ------------->[ exec B]->->->->->->

                         child                  running

 Finally, program B executes exit() and

 the return signal is sent to the parent program A

 and then program A continues on its course!

           Program A  fork        wait                         A

 Process 1  -------->  V -------->||- : - : - : - : - : - ->>----->

                       | parent          (sleeping)       ^

                       |                                  |

                       |                                  ^

                       | Program A             Program B  :

 Process 2             ------------->[ exec B]----------->X

                         child                           exit