Program running in the background

Question

Dear All, I am trying make a sign in/ sign out program at my company. There is a machine that reads magnetic cards attached to a computer. On the computer, I want to write a small program that runs in the background (not visible and does not appear in the task bar) that runs all the time waiting to read values from the standard input (keyboard or the machine). Anybody has an idea how to write this mini-program? Does it have anything to do with Console Applications? I need help Thank you