garbage collection
     n : the collection and removal of garbage [syn: garbage pickup,
          trash collection, trash pickup]

	

	garbage collection
     
         (GC) The process by which dynamically allocated
        storage is reclaimed during the execution of a program.  The
        term usually refers to automatic periodic storage reclamation
        by the garbage collector (part of the run-time system), as
        opposed to explicit code to free specific blocks of memory.
     
        Automatic garbage collection is usually triggered during
        memory allocation when the amount free memory falls below some
        threshold or after a certain number of allocations.  Normal
        execution is suspended and the garbage collector is run.
        There are many variations on this basic scheme.
     
        Languages like Lisp represent expressions as graphs built
        from cells which contain pointers and data.  These languages
        use automatic dynamic storage allocation to build
        expressions.  During the evaluation of an expression it is
        necessary to reclaim space which is used by subexpressions but
        which is no longer pointed to by anything.  This reclaimed
        memory is returned to the free memory pool for subsequent
        reallocation.
     
        Without garbage collection the program's memory requirements
        would increase monotonically throughout execution, possibly
        exceeding system limits on virtual memory size.
     
        The three main methods are mark-sweep garbage collection,
        reference counting and copying garbage collection.
     
        See also the AI koan about garbage collection.
     
        (1997-08-25)