RSTS/E version numbers

Antonio Carlini a.carlini at
Mon May 31 12:55:03 CDT 2021

On 31/05/2021 15:04, Paul Koning wrote:
> 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.
Looking at them I guess RT-11 does something similar: V2, V02B, V02C. I 
can (just about :-)) cope with the seemingly optional leading 0, but 
would there have been a V2A? There was for IAS. Actually IAS had V3, 
V3.1, V3.2, V3.2A, V3.2B and V3.2C. So IAS went major.minor in a sort of 
half-hearted way :-)

> 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.
The "80th Birthday Memo" 
( says that V1 never 
made it out of the door. V2A-19 was the first to ship.

The "DEC 1957 to he Present" book 
confirms the FY in which RSTS-11 shipped but not the version number.

The earliest manuals online seem to be the V4.x ones available on bitsavers.


Antonio Carlini
antonio at

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