IBM Selectric-based Terminals

Rich Alderson RichA at
Wed Dec 16 13:39:16 CST 2015

From: Christian Gauger-Cosgrove
Sent: Tuesday, December 15, 2015 4:25 PM

> Also, I really want one of those 2741s. Selectrics that can do I/O are
> *bleep*ing cool.

2741s are OK.  I much preferred the 2740, though.  We had those at the
Computer-Assisted Instruction Laboratory at the UTexas School of Education
(Student job, autumn 1969-autumn 1970), but only 2741s at Ohio State.

On the 2741, ETX is tied to the Return key.  That made correcting a class
of errors in Coursewriter III much harder:  Incorrectly inserted labels could
not be removed by the author, but only by a systems programmer editing the
file on disk.

On the 2740, there was a bank of 6 buttons to the upper right of the Selectric
keyboard.  I only remember 3 labels, because the other 3 didn't do anything
special under Coursewriter III or APL\360, but the important ones were EOT,
ETX, and EOB.  With judicious use of these, newlines could be inserted into the
entered text at will, allowing for the selection of labels surrounded by empty
lines.  It also allowed for security by obscurity:  The supervisor password on
the Coursewriter III system was 0x4040404040404015, which could not be entered
on a 2741.

Ah, the Good Old Days(TM)...


Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134

mailto:RichA at

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