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  Argument
 
    heap_mark    A pointer of any type, usually untyped,
                 already assigned by Mark
 
  Description
 
    The Release procedure reclaims allocated memory by resetting the
    top of the heap to the address in heap_mark. It disposes all
    memory from heap_mark to the current top of the heap. Release
    clears the entire free list; any blocks in the list are lost.
 
    The Mark procedure stores the current value of HeapPtr in
    heap_mark. The heap_mark argument is a pointer of any type,
    usually untyped. HeapPtr, a pointer variable defined in the System
    unit, always points to the top of the heap.
 
    Allocation causes the top of the heap to grow upward (toward FFFF)
    from the bottom of the heap segment. Deallocation may lower the top
    of the heap or may leave a free block in the heap.
 
    QuickPascal uses a free list to manage areas returned to the heap
    by the procedures Dispose and FreeMem. The free list is a list of
    pointers──pointed to by FreePtr──that grows downward (toward 0000)
    from the top of the heap segment. Deallocated areas below the
    current top of the heap are pointed to by pointers kept in the free
    list. GetMem and New allocate from the free list before taking any
    new memory from the heap.
 
    Release frees allocated memory above heap_mark. After the call to
    Mark, allocation of memory is above the address in heap_mark if the
    requested size could not be allocated from the free list. Release
    does not release memory allocated after the call to Mark that was
    taken from the free list and lying below heap_mark.
 
    Note that pointers to the disposed areas remain defined; however,
    they should not be used unless reallocated with GetMem or New.
 
    Release clears the entire free list, not just the pointers to
    memory it releases. Any free blocks that lie between the heap
    origin (held in the System variable HeapOrg) and heap_mark are
    lost and unavailable for later allocation.
 
    Use caution when mixing methods for deallocating variables. Dynamic
    allocation and deallocation are usually done with related pairs of
    routines. Dispose frees a variable that New allocates, and FreeMem
    frees a variable that GetMem allocates.