Future Value

I've just started studying C and i've been given a C program to write and compile but my program doesn't seem to look like anything we've studied already and their is no information in the text book, i was wondering if anyone out there could help?

The programme is Future Value,
The formula is: S=P(1+r)^n where S is the future value, P is the present value, r is the interest rate and n is the number of periods. Calculate the future value for different present values, interest rates and number of periods.

If somebody could help me get started i would really appreciate it, thanks.
:)