developed by Chuck Forsberg as the successor to
XMODEM and
was itself succeeded by
ZMODEM. XMODEM used 128-byte
packets, YMODEM can also use 1 kilobyte packets. Whereas
YMODEM is a batch protocol,
YMODEM-G is a non-stop version.
File sizes are included in the YMODEM header when sending both
binary and text files. Thus files transferred via YMODEM
should preserve their exact length. File modification times
may also be present in the YMODEM header.
YModem can
fall back to smaller packets when necessary but
there is no backward compatibility with XModem's error
detection.
[Chuck Forsberg, "XMODEM/YMODEM Protocol Reference"].
(1995-02-02)