Questions:
Here are a few simple strategies in perl: always defect, always cooperate, tit-for-tat, tat for tit?.
Your program should output one character (either c or d) per line. After the first character, your program should then go into a loop: wait for one line of input (which is the other player's first move), then output your choice for the next round.
IMPORTANT: You need to flush your output each time you print. If you don't, your output will be buffered and the tournament-running program will lock. In perl, you can do this by putting "$| = 1;" someplace near the beginning of the program. In C, you use "fflush" or the like. I'm not sure about other languages.
Your goal is to maximize the number of (discounted) points you score over the course of the entire tournament.