14 Dec
2008
14 Dec
'08
10:28 a.m.
On 10 Dec 2008 at 21:42, der Mouse wrote:
Um, if it's only six bits, it ain't ASCII;
ASCII is a seven-bit code.
(It may be a half-size subset of ASCII....)
On my old CDC Cyber 70 quick reference card, there's a nice table on
one panel with colums specifying the character, "Display" (CDC's own
code) "Hollerith" (card punch configuration) "BCD" (IBM's 6 bit
code) with two sub-columns ("Ext" and "Int" (I don't recall the
precise difference, but I believe that one was used with some of the
attached card and printer equipment and the other was used for mag
tape--maybe someone can refresh my memory). The last column is
labeled "ASCII Subset" with three sub-columns "Char", showing the
character (the 6000/Cyber 70 native character set was more of an
Algol set and lacked characters such as exclamation and quote, so
ASCII needed a different display set), "Code", the 6-bit value of the
character, and "Punch" showing the card code).
Basically, the 6-bit ASCII subset was the same as 7-bit but with bit
4 omittted. Thus, no lowercase nor control codes--e.g. the code for
the numeral "zero" was 10 (octal). This wasn't unreasonable in a day
when equipment capable of displaying lowercase alphabetics was
unusual.
Cheers,
Chuck