[ih] Origin of 'talk' command

Jerome H Saltzer Saltzer at MIT.EDU
Thu Dec 19 15:36:18 PST 2002

At 4:54 PM -0500 12/19/02, Bob Frankston wrote:
>I'd be surprised if there weren't a similar facility on CTSS (Jerry?)

There was.  See the excerpt below, from the 1965 CTSS Programmer's Guide.
The programmer's guide doesn't document any user-level commands that use
these supervisor call, but I recall using such commands.  It would require
some research to find out just when this feature first appeared in CTSS,
but from the lack of user-level commands in the programmer's guide, I would
guess that the supervisor entries were added to the system just before the
manual went to press, and the user-level commands appeared sometime after




Inter-user communication


To provide the facility for users to communicate with each other directly,
several routines have been added to the supervisor which allow the sending
and receiving of messages by way of the console input buffers. Privacy
screens have been provided which "allow" or "forbid" the sending of
messages by specified users.


To send a message:

         TSX   WRMESS,4
         PZE   =HPROBN
         PZE   =HPROGN
         PZE   LOC,,'N'

  PROBN  is the problem number of the receiver
  PROGN  is the programmer number of the receiver
    LOC  is the beginning location of the message
      n  is the number of words in the message

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