Date   : Thu, 28 Jul 1983 10:37:00 EDT
From   : Keith Petersen <W8SDZ@mit-mc>
Subject: ?modem and mdm???

XMODEM, UMODEM, MODEM2xx, MODEM7xx, MODEM9xx, TMODEM, and MDM7xx ALL
use the SAME Christensen protocol.  There are no "flavors" except for
an OPTION for using a CRC error checking mode instead of the original
CHECKSUM error checking mode.  This run-time OPTION is available in
all of the above-named programs except for UMODEM and TMODEM.

MODEM9xx is a generic MODEM7xx program for serial-port modems.  It
does NOT support the PMMI S-100 modem.

MDM711 supports PMMI S-100, D.C. Hayes "Smart Modem", U.S. Robotics
intelligent modem, AND serial port modems.  Many user overlays are
provided for easy customization of the MDM711.COM file, so it is NOT
necessary to get the .ASM file to bring up this program.  Future
support will be provided for the new PMMI MM-212 (1200 baud) S-100
modem.

MDM7xx, MODEM7xx and MODEM9xx all provide a "batch transfer" OPTION
which allows more than one file to be transferred without operator
intervention.  Again, this is an OPTION and can be considered an
extention of the Christensen protocol rather than a violation of it.
It does not have to be used.
--Keith