How to send code throw keyboard

I want to know which command I should use to send a AsCII code throw a keyboard cable.To control the PC or another devices.I want to make something like this http://pcbheaven.com/projectpages/Me..._Game_Console/ ,not the console but to simulate a key is pressed when portb1(button) is pressed.How to make that?Which comand I have to use?Thank you