[its-hackers] "ITS" pronunciation

Jack Haverty jack at 3kitty.org
Tue Sep 14 20:39:32 CEST 2021

Sounds plausible.   But that still doesn't explain the origin. I.e., did 
TK invent the name "Incompatible..." first as a "hack" on CTSS?   or did 
colloquial references to that generic timesharing system by statements 
like "It's up" or "It's down" establish ITS as the de facto name of that 
generic system, with TK inventing "Incompatible..." to explain ITS as an 

In 1967 I was taking a course in OS principles (Donovan & Madnick), 
which used the IBM system as a lab.  Can't remember if it was the 
computer running CTSS then or one running the IBM OS.  The final exam 
involved an assignment to write some code to do something in the OS (all 
on punch cards of course).  The grading program would load each 
student's code and execute it within the OS, and create a grade based on 
the observed results.

There were two legitimate ways to get an A:  1) do the assignment and 
write code that worked, or 2) write code to hack the grading program so 
it thought, incorrectly, that your code had done the assignment 
properly.   Such was the philosophy of hacking that was good preparation 
for getting into the ITS environment a few years later.


On 9/14/21 11:14 AM, Lars Brinkhoff wrote:
> Jack Haverty wrote:
>> I don't remember any pronunciation other than "its" being used at
>> all.   Never "eye-tee-ess".
> Thanks, I think that's really interesting!  ITS (forced pun intended)
> the operating system that keeps delivering juicy tidbits.
>> I recall asking what "its" meant and hearing the plausible story that
>> it represented a play on words as a competitor to the "official" MIT
>> timesharing utility - CTSS, the Compatible Time Sharing System.  ITS
>> was created as the "Incompatible Time Sharing system".
> I think it's fairly well established that Tom Knight invented this name.
> In AI memos from early 1967, it's referred to as the generic "time-
> sharing system", or just TS.  The first mention by name I have found is
> in AI memo 146 from October that year: "PICPAC is a PDP-6 program to be
> used for manipulating picures of real-world scenes. It operates under
> ITS (Incompatible Time-Sharing System)".

More information about the its-hackers mailing list