Reading through manuals is neither fun nor all-enlightening. It will still take a lot of time usually to find out WTH has gone wrong.
You might wonder why there are tutorials in some games and applications...
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.