Example of Function stubs:
The three functions have not so far been written, though, therefore the function stubs are put in place so that the script can be executed and tested. The function stubs consist of the appropriate function headers, followed by the simulation of what the function will ultimately do (example, it puts random values in for the output arguments).
Then, the functions can be debugged and written at the same time. It is much simpler to write a working program by using this method than to try to write everything at once-then, whenever errors occur, it is not always simple to determine where the problem is!