RSTS/E version numbers

Paul Koning paulkoning at
Mon May 31 09:04:08 CDT 2021

> On May 31, 2021, at 8:06 AM, Antonio Carlini via cctalk <cctalk at> wrote:
> Can someone explain RSTS/E version numbers to me?
> They seem to be all over the place: V2A-19, V4A-12, V4B-17, V5A-21, V5B-24, V5C-01, V6A-02, V6B-02, V6C-03.
> Then it seems to have switched scheme but the "-number" suffix reappears: V7.0, V7.2, V8.0-06.
> Any clarification would be helpful.

I think this might have been part of a general DEC change in version numbering conventions. 

The earlier rule was that the first number is the major version, the letter is the minor version.  As of V7 it changed to major number dot minor number.  In either case, the dash number suffix is the baselevel number (development build cycle number).  Those typically restart at 0 or 1 for each release, so V5C-01 indicates only one baselevel was done for that minor release.  That may not be true in all cases; I doubt that V4B had 17 baselevels so that number probably wasn't reset between V4A and V4B.

The definition of "minor release" was not always applied consistently.  For example, V6B was the first release that was built natively (using RT-11 emulation) rather than using DOS.  And its the first release that did bus probing at startup to figure out the peripheral configuration and adjust the running monitor to match.  That seems like a pretty large change, but for some reason it didn't prompt a new major number.

The notation change happened part way through the V7.0 development cycle.  I remember a memo from management entitled "RSTS V7A canceled" :-) .

Sometimes version numbers seem to be missing.  I don't know if anyone ever saw V1, and I also never saw V3B though I have seen V3A and V3C.


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