[geeks] Oldest OS Still Developed

[Sridhar Ayengar]

Charles Shannon Hendrix wrote:
>>> 	- MVS
>> Early to mid 1960's 
> 
> No, it was not released until 1974.

Wrong.  Look at MVT or even MFT from which it evolved.

>>> 	- DOS/VE (I *think* it is still developed)
>> I think it post dates OS/360 from which MVS derives, but I am not sure.
>> By 1969 you had TOS (which I think was no longer supported), DOS, OS/360,
>> ACP and VM/360.
> 
> DOS/VSE (*) is 41 years old this year, so that puts it at 1965.
> 
> * I think this is the right name, not DOS/VE, unless both were used.

*VSE* is, but OS came out some time before.

>> OS/360 still lives on as MVS, VM is still around, but most of it migrated
>> to hardware in the late 1980s. I don't know if anyone still uses ACP, 
>> and I have never seen a TOS system, but I have been using 360's (and on)
>> since the late 1960s.
> 
> IBM just recently made DOS/VSE (z/VSE) a 64-bit OS. They acknowledge it
> won't actually help much since most VSE programs are 24-bit, but it does
> allow z systems to run them in 64-bit address spaces.
> 
> The next version of DOS/VSE will require a 64-bit machine, which will
> end-of-life support for 31-bit systems that are still running.
> 
> IBM must hold the record for how long they'll support a system.

That's only the half of it.  A 1966-vintage MFT program will happily run 
under the latest z/OS *without recompilation*.

>>> 	- RT/11
>> PDP-11s? New hardware my friend. :-) Weren't they the first machines to use
>> that silly reversed byte order?
> 
> RT/11 is an old OS now, but I believe some clone PDP-11 systems still
> use it.
> 
> Seems like it qualifies to me.

It would if it were anywhere near as old as VSE or TOPS-10.

Peace...  Sridhar