3Com U.S. Robotics 56K Winmodem Manual page 52

V.90
The ITU-T standard for 56 Kbps modem
communications.
Xmodem
The first of a family of error control
software protocols used to transfer files
between modems. These protocols are in
the public domain and are available from
many bulletin board services.
XON/XOFF
Standard ASCII control characters used to
tell an intelligent device to stop/resume
transmitting data.
50
G G G G
LOSSARY LOSSARY LOSSARY LOSSARY
Ymodem
An error-checking protocol that can send
several files of data at a time in 1024-byte
(1K) blocks. This protocol can use either
checksums or CRC for error checking.
Ymodem G
This is similar to the Ymodem, except it
relies on the modem for error checking,
which makes it faster.
Zmodem
This is similar to Xmodem and Ymodem,
except it includes batch transfer, the ability
to recover from a partially complete
transfer, an autostart feature, and improved
efficiency.