Compute the hypotenuse of a right angled triangle, with input validation.
(If you were logged in as a student, you could submit an exercise solution, and get some feedback.)
DRY stands for Don't Repeat Yourself. One of the Big Ideas of programming.
So far, each of the subs has been called just once per program. Let's do something different.
Remember that strange tax return program? The worksheet:
Let's add input validation.