Recipe system.

Can anybody here guide me on how do I make a recipe system? Like most of the recipe system found over here like Artifical's recipe system.

I know I have to use structs to store the integer item in slot 1 to 6.

It would be nice if anybody here could test me how to do this as I don't want to use a recipe system by another, I like to learn instead of using other people's code. I will be a dedicated listener if u tell me how , at least just give me the starting path on how to create it