Only on some systems, commonly in a header named conio
Why does it make my program error?
Because your system doesn't have it, or you haven't included the header, or you haven't linked to the right library, or because you spelled it wrongly, or because it's broken on your system, or for any one of a million different reasons. We're not psychic and coming here saying "why doesn't my program work" without providing so much as a single error message is really not helpful.