Okay, things you
need to know to write a game include general program logic and basic I/O (you need input from the user, after all). You also need to learn how to validate that input, so that your program doesn't puke on its shoes when the user does something 'wrong' (which users do quite often).
Other things that you will likely need to learn are:
- File handling- otherwise, you cannot save/load games, high scores, etc, or dynamically load graphics at runtime- in other words, all the graphics would need to be embedded in the .EXE, which is generally an inflexible approach)
- Graphics- depending on the type of game; text adventures, for example, don't need graphics, but the vast majority of games today make heavy use of them. Also, how you handle graphics varies from system to system, and even on one system, there are various ways to do it.
- Sound- most games also rely heavily on digital sound effects and music. Like graphics programming, sound programming is highly dependant on the target platform.
- Data structures- things like linked lists, binary search trees, and the like. These are important in most games programming, just as they are in regular applications or systems programming, but in games, there is an emphasis on choosing the fastest algorithms, so even if you don't learn to write your own, you at least need to learn how to pick the most appropriate ones to use.
So, as you can see, there's lots to learn, especially for games programming. Besides, as to your original question, maybe if you offered a little more information (what kind of game, etc), it would help.