> excellent for the phone lines it was used for Unfortunately it was not. Thus, YMODEM and ZMODEM replaced it. ZMODEM is more complex, more reliable. YMODEM is

> excellent for the phone lines it was used for Unfortunately it was not. Thus, YMODEM and ZMODEM replaced it. ZMODEM is more complex, more reliable. YMODEM is same as XMODEM, but bigger buffer if I recall correctly. XMODEM is “simple” implementation, but maybe not “fast” or even “low cost” implementation due to time needed to debug its issues :(