[ih] Instant messaging, was We can hang up now, it's all done.

[John Levine]

>The first instance of this type of capability in a commercial system  
>appears to be IBM's CP/67 Release 3 (approximately November 1970) in  
>the CP "MSG" command.

When I was in high school I was able to use the dial-in time-sharing
service from Applied Logic, a local service bureau that ran first on a
PDP-6 and later PDP-10 in Princeton NJ, using heavily modified
versions of DEC's operating system later known as TOPS-10.

They had a TALK command at least as early as 1968 that let you type
from one terminal to another, which would be a candidate for first
commercial offering.  I recall using it to ask the operator to set
aside printouts so I could bike over after school and pick them up.

R's,
John