[TUHS] PDP-11, Unix, octal?

[beebe@math.utah.edu (Nelson H. F. Beebe)]

Joerg Schilling asks today:

>> this has been done with 10 6 bit chars in a 60 bit word.
>> Did people use octal in this area?

I worked on a CDC 6400 with both NOS and KRONOS operating systems in
the 1970s.  The 6400/6600/7600 family were definitely in the octal
world.  Initially, the character set was 6-bit, with one character
reserved as an escape to mean that the next 6-bit chunk was to be
included, giving a 12-bit representation that added support for
lowercase letters (a feature that we could only get on our IBM 360 and
Amdahl 470 mainframes with a once-a-night change of the line printer
glyph chain).

Here is a quote by the lead architect, James E. Thornton, who wrote
the 1970 book, ``Design of a Computer: the Control Data 6600'', and
the 1980 history paper ``The CDC 6600 Project''
(http://dx.doi.org/10.1109/MAHC.1980.10044):

>> The selection of 60-bit word length came after a lengthy
>> investigation into the possibility of 64 bits.  Without going
>> into it in depth, our octal background got the upper hand.

That comes from page 347 of the paper.

-------------------------------------------------------------------------------
- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- University of Utah                    FAX: +1 801 581 4148                  -
- Department of Mathematics, 110 LCB    Internet e-mail: beebe at math.utah.edu  -
- 155 S 1400 E RM 233                       beebe at acm.org  beebe at computer.org -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -
-------------------------------------------------------------------------------