[Simh] UNIT_RO in simulated units

[Mark Pizzolato]

On Sunday, March 25, 2018 at 5:14 PM, Bob Supnik wrote:
> Again, the question is whether you want them to be "read only" to the device
> simulator or to SCP itself.
> 
> Typically, I've wanted paper-tape readers to respond to DEPOSIT, so that I can
> make changes or corrections to an input file. The "read only"
> nature of a paper-tape reader comes from the device simulator not having any
> code to write to the associated file. If you want to block DEPOSIT, then what
> you suggest is the correct course of action.

Actually, if you never care to use deposit to edit files, then UNIT_RO without 
UNIT_ROABLE statically set will only open files "rb".  The thing that started this
was work on card readers which are certainly never writable, AND attempting 
to edit card image files with deposit commands seems like a steep uphill climb. :-)

- Mark

> On 3/25/2018 8:08 PM, Paul Koning wrote:
> >
> >> On Mar 25, 2018, at 7:23 PM, Bob Supnik <bob at supnik.org> wrote:
> >>
> >> Mark Pizzolato pointed out that UNIT_RO is cleared unconditionally at
> DETACH. This makes static declaration of a unit as UNIT_RO impossible. He has
> proposed a change to distinguish a "static" read-only unit (UNIT_RO set but not
> UNIT_ROABLE) from the usual "dynamic" read-only, set by ATTACH -R or by a
> unit-specific SET command.
> > So how does one deal with things like paper tape readers, which are by
> defition read-only?  I've handled that by marking them ROABLE and supplying
> the R switch in the attach handler.
> >
> > 	paul