29 August 2018 08:30:00 AM

NOT_ALLOCATED_ARRAYS
  C version

  When an array starts out as a pointer, you have to use the
  MALLOC command to allocate memory.  You should always 
  initialize such array pointers to NULL, so you can tell if
  they've been allocated or not!

  Unfortunately, when you FREE an array, you also have to
  reset the pointer to NULL; that does not happen
  automatically either!

  The pointer A is not preset to NULL.
  Before allocation, we check the value:
    a = (nil)
  The test 'if ( !a )' is not guaranteed to return 1
  because we did not initialize A properly.
    !a = 1
  Now we allocate A.
    a = 0x1cc90e0
    !a = 0
  Now we FREE A.
    a = 0x1cc90e0
    !a = 0
  Now we RESET A to NULL!
    a = (nil)
    !a = 1

  The pointer B is preset to NULL.
  Before allocation, we check the value:
    b = (nil)
  The test 'if ( !b )' is guaranteed to return 1
  because we initialized B properly.
    !b = 1
  Now we allocate B.
    b = 0x1cc90e0
    !b = 0
  Now we FREE B.
    b = 0x1cc90e0
    !b = 0
  Now we RESET B to NULL!
    b = (nil)
    !b = 1

NOT_ALLOCATED_ARRAYS:
  Normal end of execution.

29 August 2018 08:30:00 AM