Zmodem's code is uglier than Kermit's IMO. Gods help you if you have to read either, but Kermit is written better and EK is almost understandable once you fold

Zmodem's code is uglier than Kermit's IMO. Gods help you if you have to read either, but Kermit is written better and EK is almost understandable once you fold all unneeded #define's. I'm surprised no-one mentioned the venerable UUCP. It has more variants than X/Y/Zmodem combined: at least 12.