Murray Lesser wrote to Roy J. Tellason on 08-29-1999

ML>    Ctrl-Z (1fh) has been part of the ASCII 7-bit code since its
ML> beginning (around 1960, IIRC).  The first three of the four
ML> "separator" control characters, 1ch through 1eh (, , and
ML> ) were originally intended for data transmission segment
ML> separators.  IIRC, Ctrl-Z  was the "user-defined separator" to be used 
in other
ML> environments.  IMO, ASCII was originally devised to accommodate
ML> AT&T, who realized that the 5-bit Baudot code (used previously for
ML> TTY systems) was no longer sufficient for "modern" data
ML> transmission.  The computer manufacturers were snookered into going
ML> along with the 7-bit idea, because (at the time) nobody (except IBM)
ML> was contemplating any computer character codes having more than six
ML> bits (and IBM wasn't making public noises about System/360 at the
ML> time).  Later, Ctrl-Z was a convention adopted by the computer
ML> manufacturers as an EOF mark for the new 8-bit tape-drive systems. 

These codes were also implemented by certain terminals, such as the
TTY Model 33 and 34 which had paper tape punches.  They served to
generate leaders, tear lines, etc. to the best of my recollection. 
Along with the 'BELL' command and a few others they were command and
control operators. They were also used as rudimentary steering
commands, so they did have a real use - thankfully long since
abandoned.

Will Honea 
--- Maximus/2 2.02