Problem with programming with functions

I am facing a lot of problems with c programming with functions. In particular I could not solve a very simple problem of calculating x^y using functions.But I do not want it using the <math.h> and power function. If anyone can provide its solution with proper explanation it will be very helpful for me. The books I have come across are not very helpful. The name of any good book or any other reference will also be very helpful to me.

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> The books I have come across are not very helpful. The name of any good book or any other reference will also be very helpful to me.
Books teach the language (to varying degrees of fidelity), and probably explain some of the more basic standard library functions.

To see the full extent of functions for your compiler, you should read the local manual pages (or help files).