Pet peeve time: "code" in the software sense is a mass noun, not a collective noun. It has no plural. You don't eat "an oatmeal" or several "oatmeals", you eat oatmeal. In the same way, you don't write "a code" or "codes", you write code. If you mean a unified body of code that can be run independently, you might say you're writing a program or several programs, but "code" is just the undifferentiated mass of stuff which is the subject of programming. It is stuff that you write, not a thing that you write.