Wat (wie) is XMODEM - definitie

FILE TRANSFER PROTOCOL

XMODEM-1K; WXMODEM; Xmodem; XModem; WXmodem; Wxmodem; MODEM7; NMODEM; X-MODEM; Batch XMODEM; Modem7 batch

XMODEM

<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)

XMODEM-1K

A version of XMODEM using 1 kilobyte packets.

MODEM7

A batch file transfer protocol. See also XMODEM. (1995-05-02)

Wikipedia

XMODEM

XMODEM is a simple file transfer protocol developed as a quick hack by Ward Christensen for use in his 1977 MODEM.ASM terminal program. It allowed users to transmit files between their computers when both sides used MODEM. Keith Petersen made a minor update to always turn on "quiet mode", and called the result XMODEM.

XMODEM, like most file transfer protocols, breaks up the original data into a series of "packets" that are sent to the receiver, along with additional information allowing the receiver to determine whether that packet was correctly received. If an error is detected, the receiver requests that the packet be re-sent. A string of bad packets causes the transfer to abort.

XMODEM became extremely popular in the early bulletin board system (BBS) market, largely because it was simple to implement. It was also fairly inefficient, and as modem speeds increased, this problem led to the development of a number of modified versions of XMODEM to improve performance or address other problems with the protocol. Christensen believed his original XMODEM to be "the single most modified program in computing history".

Chuck Forsberg collected a number of common modifications into his YMODEM protocol, but poor implementation led to a further fracturing before they were re-unified by his later ZMODEM protocol. ZMODEM became very popular, but never completely replaced XMODEM in the BBS market.

https://en.wikipedia.org/wiki/XMODEM