Source : Free On-Line Dictionary of Computing

bread crumbs
     
        Debugging statements inserted into a program that emit output
        or log indicators of the program's {state} to a file so you
        can see where it dies or pin down the cause of surprising
        behaviour.  The term is probably a reference to the Hansel and
        Gretel story from the Brothers Grimm; in several variants, a
        character leaves a trail of bread crumbs so as not to get lost
        in the woods.
     
        [{Jargon File}]