4 Top down isn't everything!

Although top-down design is taught in every algorithm design class and throughout all computer courses, it is not the only way to write programs. It is nearly impossible to apply the top-down method perfectly in the real world.

In other words, it is nearly impossible to use the correct abstract operations to make the top level algorithm ``just right'' when you are writing an algorithm (or a program). In real life, programmers rely on a few techniques to keep program code manageable.