You must not recursively call main. Not just in your release program, but in any code. Things can go wrong if you do. Therefore, you should use a loop instead.
Originally Posted by Adak
io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
Originally Posted by Salem
You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.
Outside of your DOS world, your header file is meaningless.