I am writing a trainer for a flash game, but I'm a little confused. Every single function/tutorial I looked at uses windows.h dependencies, which obviously isn't available on Mac. Are there any ways to select a process ID and edit a certain address's value?
If you want to change another process' memory you may use shared memory. It allows mapping of some piecees of memory into the address space of multiple simultaneously running processes. See shmat(2) and others.