

                                   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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