Question on maxima programming



I have written up a simple program:

/*Area of a circle test program
*/
/*Michael Carey, mpc20 at bigpond.com
*/


read("Enter the radius:");

%^2 * pi;

And want to convert it to use local variables. Is this possible?
Say it reads the input into a variable and can be used though the rest
of the program.

Also is there a good programming guide for maxima?

Cheers Mick C