Circle Calculator Help

[Alexander]

By the way, this is just my 2nd program in D.
It is just for fun, and I'm doing it to practice using this 
language.

This is normally how I teach myself languages.
I write a simple one then a more complex one on and on until I'm 
fluent in the language.
I don't have the book (but I'll get it soon), and I've just tried 
to use online references for this so far.

Thanks again!