Founder of the CBBS bulletin board, the first bulletin board system (BBS) ever brought online, Christensen started development during a blizzard in Chicago, Illinois, and officially established CBBS four weeks later, on February 16, 1978.
He was noted for building software tools for his needs. Christensen wrote a cassette-based operating system before floppies and hard disks were common. When he lost track of the source code for some programs, he wrote ReSource, an iterative disassembler for the Intel 8080, to help him regenerate the source code. When he needed to send files to Randy Suess, Christensen wrote XMODEM.
He received two 1992 Dvorak Awards for Excellence in Telecommunications, one with Randy Seuss for developing the first BBS, and a lifetime achievement award "for outstanding contributions to PC telecommunications." In 1993 he received the Pioneer Award from the Electronic Frontier Foundation. Christensen worked for IBM as a technical sales specialist from 1968.
