The Free On-line Dictionary of Computing (30 December 2018):

Ward Christensen

    The inventor of XMODEM and of the BBS.  Ward did
   physics in college and programmed mainframes for IBM.

   Ward and friend Randy Suess set up their BBS on first on
   1978-02-16 in Chicago.  It ran on an S-100 computer with 64k
   RAM and two single-sided 8" 250kB diskettes.

   Freeware Hall of Fame
   (http://freewarehof.org/ward.html).

   (2005-09-20)