[Info-vax] date comparison format from a program

[Hans Bachner]

Dave Froble schrieb am 21.05.2019 um 16:43:
> [...]
>
> Now, I may be wrong, same old territory for me, but, if I was designing
> something that had to last for a long time, I'd design it with "black
> boxes" that perform a task, but can be replaced (inside the box) with
> newer stuff.  As long as the "box" did what it was suppose to do, so
> what?  More viable, probably cheaper.
>
> [...]

Well, this is exactly what an emulator like CHARON-VAX does.

(Open)VMS accesses a "black box" which can be a physical VAX or an 
emulated VAX. As long as both (re)act identically to any given input 
(e.g. a driver sending some signal to a storage controller), everything 
is fine.

As I mentioned Stromasys licensed hardware diagnostic routines from DEC 
to verify that you can't tell what's in the "black box". As long as a 
"black box" is certified for a given application (and not the components 
inside the box), replacement of physical hardware with an emulator is 
not an issue. There are quite some cases where the emulator was accepted 
by the certification authorities.

Hans.