Firstly... an unsigned char will give you a max result of 255. You would be better off with an unsigned int.
Secondly.. simple maths will get the result into the array. Then you need a lookup table to identify which bits light each segment on the display.
If you look at my signature at the bottom of my post, you'll see two links.. One is Nigels tutorials in ASM where you will find a schematic using 7 segment display's, and one is mine, using C to run on Nigels tutorial boards..