Top-down implementation is the implementation
analogue of top-down design and stepwise refinement. It
supports incremental program development by allowing for
error and improvement.
A stripped-down, skeletal version of main()is
written. It doesn't have to implement all of the details of
an algorithm or fulfill the all of the program requirements.
It does contain, in a form that can be
compiled and run, rough versions of all the functions and
their parameter lists. These are known as stub functions.