Hmm... this could be hard, or it could be easy. If it's a function that ONLY regulates the temperature, getting all of the data from other sources, it could be 1 page. If those other functions are being printed, well, you may need several reams of paper. It also depends on the programming language used. Something like this, I'm guessing possibly COBOL, which is a bloated language in itself. A function in COBOL, even one this simple, can take 2-3 pages. The pages, in this case, would be printed in landscape (length-wise instead of width, like everyone is used to).

"You need me. You wouldn't be much of a hero without a villain. And you do love being the hero, don't you. The cheering children, the swooning women, you love it so much, it's made you my most reliable accomplice." -- Lex Luthor to Superman, Question Authority, Justice League Unlimited