TOPS-20 interrupts

[JONL at MIT-MC (Jon L White)]

MACLISP is advertised to have interrupt meaning for the following
control characters:
  ^A, ^B, ^C, ^D, ^G, ^R, ^T, ^V, ^W, ^X, and ^Z
I believe that ^Q, ^S, are macro characters, and ^K and ^L are specially
recognized by the read-scanner.  Apparently there are two bugs here?
1) on ITS systems, ^S fails to set ^Q to (), and
2) on TOPS-20, ^Q seems to be set up as an interrupt character.
3) on neither system does ^A set the value of ^A as it should.
Having interrupt capacity for at least
  ^B, ^G, ^V, ^W, ^X and ^Z
would be fairly important for TOPS-20 maclisps.

Now there seems also to be a bug in (SSTATUS LINMO T) on the TOPS-20
systems - it affects TLPRIN, but seems not to effect the ruubout scanner.
It woudl be possible to use the standard TOPS-20 JSYS for input, thereby
taking adavantage of all the twenex terminal niceities, if the LINEMODE
worked ok; but when not in linemode, lisp must inspect each character in
order to decide if enough has been buffered up.