> On Dec 17, 2018, at 2:44 PM, Phil Budne <[email protected]> wrote:
>
> Clem Cole wrote:
>> .... In the old days, the idea of 'access
>> methods' was the natural ways OS's did I/O and RMS was VMS's answer.
>
> Using RMS as the primary way to do file access was dain bramage unique
> (at DEC) to VMS, no?
Not unique to VMS nor even to DEC. There was RMS-11 in PDP-11 operating
systems. I have the impression that predated VMS, though I may be off a bit.
RMS-11 always felt like an extension of FCS-11, the RSX file structure library
that introduced such things as file attributes and variable length records.
But this stuff is much older. RMS feels a lot like the various "access
methods" IBM created in OS/360. Fixed length records, variable length records,
the notion of "spanned" records (records that cross block boundaries) and
indexed files all appear in OS/360 well before VMS appeared.
I think similar stuff existed elsewhere. CDC had record stuff in the 6000
series mainframes, though that felt more like an add-on, one I never used. But
apart from that, they did have files with internal structure, called "records"
and "files", rather different from what OS/360 did. So the notion of a file
being a lot more than just a vector of bytes is quite old.
One odd thing about IBM is that some of the access method mechanisms relied on
hardware capabilities. For ISAM files, you'd write the file data with key
fields in each sector, and use the search for key match feature in the disk
drives (to find the matching sector so long as you knew on which track to
look). That seems to be pretty unusual, though I've also seen it done by
Electrologica in Holland in the mid 1960s.
paul
_______________________________________________
Simh mailing list
[email protected]
http://mailman.trailing-edge.com/mailman/listinfo/simh
