Chuck Forsberg

Chuck Forsberg's fame comes in part from developing YMODEM and ZMODEM. ZMODEM is a file transfer protocol with error checking and crash recovery. ZMODEM does not wait for positive acknowledgement after each block is sent, but rather sends blocks in rapid succession. If a ZMODEM transfer is cancelled or interrupted for any reason, the transfer can be resurrected later and the previously transferred information need not be resent.

Chuck Forsberg designed YMODEM as a file transfer protocol for use between modems and developed it as the successor to XMODEM and MODEM7, It was formally given the name "YMODEM" (Yet another Modem implementation) in 1985 by Ward Christensen.