Vital that you understand this

It is vital that you understand this program organization before leaving this lesson.

If you don't understand it, please continue to ask questions until you do understand it.

Why is it so vital?

Understanding this program organization is vital in order for you to be able to progress from this course in Programming Fundamentals to the world of Object Oriented Programming (OOP).

An understanding of this program organization is fundamental to the new world of programming that depends heavily on OOP.