GENWiki

                                 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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