[Simh] Transferring the licence file to the VAX emulator

[Paul Koning]

> On Dec 17, 2018, at 2:44 PM, Phil Budne <phil at ultimate.com> 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