Inputting into another program (C/C++)

So, how do you do it? I'm trying to create a NetHack character generator, but for that I need my program to input text into it in a predetermined way. Everything I read about interprocess/interprogram communication is far too complex for what I need, I'd rather start slowly and then go building up the concepts. Finally, cheating is not my main concern here (changing the source would be much easier), learning is, so don't go crazy because I asked!

>>5
Ok then, at least you clarified some things.

>>6
First thing I tried, but didn't work. When you do that, nethack stops receiving input (what you type doesn't appear on the screen), and the only thing you can do is quit with ^c.