Which paper tape hole is bit 1? - test-drb@ccmp.vtda.org

20 Nov 2005

On Nov 19 2005,  9:58, Paul Koning wrote:
...

>>>> "Barry" == Barry Watzman <Watzman at neo.rr.com> writes:

  Barry> However, one question, this chart shows the high-order bit
  Barry> (parity bit) punched for every character, no exceptions.  Was
  Barry> that a standard convention in sending ascii files to paper
  Barry> tape?

 You mean the high order bit was always on -- as opposed to being a
 parity bit?  That's unusual.  Parity is a bit more common, but I don't
...
  think there was a single standard.  Classic ASCII is a
7-bit code,
 leaving the 8th bit for people to mess with as they saw fit. 
It's called "mark parity", though it's not really a parity indicator at
all, just a way of defining that that bit is always set.  It's exactly
equivalent to having 7-bit data with an extra stop bit and not unusual
at all on PDP-8s, in fact it's the norm.  All DEC-supplied ASR33s were
set for mark parity, as far as I know.

-- 
Pete						Peter Turnbull
						Network Manager
						University of York