YMODEM

A file transfer protocol used between modems. YMODEM was

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)