xmodem

Computing Dictionary

XMODEM definition

communications
Ward Christensen's file transfer protocol, probably the most widely available protocol used for file transfer over serial lines (e.g. between modems). XMODEM uses 128-byte packets with error detection, allowing the receiver to request retransmission of a corrupted packet. XModem is fairly slow but reliable.
Several variations have been proposed with increasing packet sizes (e.g. XMODEM-1K) and different error detection (CRC instead of checksum) to take advantage of faster modems. Sending and receiving programs can negotiate to establish the best protocol they both support.
John Mahr wrote the original XMODEM CRC error correction code. This implementation was backward compatible with Christensen's original checksum code. It improved the error detection from 98% to 99.97% and improved the reliability of transmitting binary files.
Standard XMODEM specifies a one-second timeout during the reception of characters in the data block portion of a packet.
Chuck Forsberg improved upon XMODEM by developing YMODEM and ZMODEM.
[Chuck Forsberg, "XMODEM/YMODEM Protocol Reference"].
(2005-09-16)
The Free On-line Dictionary of Computing, © Denis Howe 2010 http://foldoc.org
Cite This Source
Explore Dictionary.com
Previous Definition: xmm
Next Definition: xmodem-1k
Words Near: xmodem
More from Thesaurus.com
Synonyms and Antonyms for xmodem
More from Reference.com
Search for articles containing xmodem
More from Dictionary.com Translator
Dictionary.com Word FAQs

Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.

Nearby Words
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature