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Why can the stack avoid the overwrite problem ???

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• Terminology: active function/method
  • Active method/function:

    Active method/function = the method/function that is executing

    Note:

    Only the method that is invoked last is active !!!

    Example:

    If main( ) calls A( ) and A( ) calls B( ), then: B( ) is active main( ) and A( ) are inactive

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• How the program stack avoids the overwrite problem in parameters passing and storing local variables
  • Property of a stack:

    A stack will grow when things are pushed on the stack (That is as long as there are available memory space left)        The new things pushed on the stack will not overwrite the old things inside the stack !!!

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  • Example:

    When main( ) passes parameters to A( ) and A( ) creates its local variables using the stack, we will create a stack frame for A( ): Then if A( ) passes parameters to another function B( ) and B( ) creates its local variables using the stack, we will create another stack frame (on top of A's stack frame) for B( ):

    So this is how a stack can avoid the overwriting problem of registers !!!!