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CTTY.DOC
I asked around about the DOS 2.0/2.1 function CTTY and could
not find anyone familiar with it. So I put on my hacker's cap
and "went to it." (After midnight, in true hacking style.)
The DOS manual explains that the command is simply CTTY
device-name. This will transfer control from the keyboard and
screen to that device. It suggests that LPT1: is not a good
idea since the printer communicates (mostly) one way. What
this really leaves is COM1:, COM2: and AUX: (Whatever AUX:
is! [I'd love to hear from someone about AUX:])
I very cleverly tried typing CTTY COM1: It does do something,
it kills the keyboard and a cold BOOT is necessary to
restart. Well, that wasn't it. Something must occur prior to
the CTTY command. Being strictly a seat-of-the-pants type, I
set the HAYES to ANSWER and called in. Nice, I had a
connection (CARRIER/carrier). I rushed over to the PC
keyboard and typed CTTY COM1: and the screen went dead. So,
what else is new....but, on my other SYSTEM, (other end of
the office), the prompt A> appeared. I sat and typed on the
terminal just as though I was sitting in front of the IBM.
Well, what do you know?
1) Commands are limited to what the terminal keyboard can
reproduce i.e. ^C for CTRL-BREAK but not CTRL-ALT-DEL (as if
you would want that one anyway).
2) Going to BASIC cuts you off. SYSTEM control returns to the
keyboard.
3) Most commands work except COPY as it relates to CON: or
COM1: COPY from disk to disk worked O.K.
4) This means is total control from outside while in DOS only
on a line-by-line basis. Anything which relies on screen
mapping will not work. (I ran Norton's DISKMAP from the
terminal and the map appeared on the PC screen.)
Now...
You may be wondering why all this verbage. Well.... the
result of my efforts is a BASIC program called RING.BAS which
will set up the HAYES to patiently look for an incoming ring,
and very politely turn SYSTEM control over to the caller. Oh,
I forgot to mention the BASIC program must be called from a
BATCH file called OUTSIDER.BAT. When RING goes back to the
SYSTEM, the next command is CTTY COM1: Slick, huh? RING will
even write the BATCH file for you. Just take a look at the
internal documentation for additional information. The
program is not fancy and I can think of lots to add to it,
but I am sure you can too.....
Dan Derrick 2/21/84 70215,1136
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