Around 1988 or maybe it was 1989, we were using glass tty terminals (e.g., vt100s) connected to the ECN Encore MultiMax server at the University of Oklahoma in Norman, and there were so many students all trying to use the terminals that it was possible to go there, find a terminal, have to go to the bathroom, and then it would be taken by someone else when you got back. I was tired of always having to fight for a terminal.<p>I knew of some other students that were using simple terminal lock programs, but I wasn't impressed. I wanted something that was able of doing more, and with more configuration options. In the end, mine could give you a countdown timer to when your lock would expire and the next person could log in (maximum of 45 minutes for us regular students, which wasn't quite long enough to grab a terminal, go to class, and then come back and still have it locked), it could run a program of your choice every time it updated the screen (e.g., print out a fresh fortune every minute), and could even display simple character mode graphics that you stored in a file. It could be configured via the command line, environment variables, or a configuration file.<p>In the end, virtually everyone at OU in the EE/CS program was using it, and I contributed my sources to comp.lang.sources.c and comp.Unix, or something like that.<p>I found out that some of the senior system admins on those computer systems did not use my program, because they knew what system calls I was using, and they knew of some kernel bugs that could be exploited to cause the program to exit without actually logging you out. But I think they were the only ones who weren't using my "tl" program.<p>I think that may have been the last time I did anything I consider to be real, serious, programming. I've hacked on stuff since then, but nothing like that.