[GreenKeys] M33 disable printing when punching?

[Douglas W. Jones]

On Aug 20, 2008, at 10:33 AM, Chris Elmquist wrote:

> Is there a mod or recommended practice for disabling printing when the
> M33's punch is enabled?

I recall that Honeywell (or the predecessor of their minicomputer
division, CCC -- Computer Control Corporation) must have been concerned
about this in the 1960's, because they designed the object code format
(the binary format used by assembly output) for the DDP 615 (formerly
the CCC 516) so that it was entirely non-printing.  As a result, you
could read object code paper tapes on a M33 without wasting paper or
ribbon.  There was plenty of clatter, though.

I wish I could remember more about the format, I think they used what
would later be designated as the lower-case block of ASCII characters
to get 5 bits of data per character, with a few otherwise unused
control characters substituted in for rubout and a few other codes
they didn't want to trample.

During assembly, before printing a line of listing, the assembler would
output an XON, object code, and XOF, so the object tape and listing were
both output to the M33 at the same time, again, with no nonsense printed
in the listing as the binary code went by, just lots of noise.

I thought the whole thing was very clever, but it wold have been nicer
if there were something analogous to XON XOF to turn on and off the
printer as well as the device control characters for the reader and
punch.

		Doug Jones
		jones at cs.uiowa.edu