The command to communicate with another user is called TALK.  Its
argument is either the programmer name of the person you want to
talk to, the device name of the terminal you want to talk to, or
an ARPAnet address.  For example:

	TALK MRC
	TALK TTY34
	TALK Ellen@MC  (% is legal as a host name delimiter also).

The command will fail for any of the following reasons:

. user not logged in (use MAIL)
. user logged in more than once (use a terminal instead of a user spec)
. user gagged or (for ARPAnet TALK) refusing links (use MAIL)
. the ARPAnet site is unreachable or does not support network linking

When you are in a (local) talk ring, what you type goes only to the
terminals in the ring, not to the monitor or a user program.  To leave the
talk ring, type [CALL] (control-C from non-displays).

TALKing to local users does not require login, and does not run a program,
hence the core image is preserved.

TALKing to network users requires login and runs a program.  To leave
network talk, type <CONTROL><META>[LF] (control-Z from non-displays).

It is considered antisocial to use the TALK command to establish
communication with strangers.  A better way is the SEND command, which
will send a message to a user but does not interfere with his work.
Type "HELP SEND" for more info.