Date   : Tue, 12 Apr 1988 10:02:51 PDT
From   : Bridger Mitchell <bridger%rcc@rand-unix.ARPA>
Subject: CP/M 2.2 PUBlic files

Brian R. Lair asks if there is a way to access user-0 SYStem
files in read-only mode from another user number.

If the need is only for LOADING COM files (by the command processor)
from other user numbers, then the ZCPR3... search path will do the job
nicely.  If you want PROGRAMS to have automatic access to files in
other user numbers, more is needed.

In my Dr. Dobbs' Journal article (CP/M 2.2 Goes PUBlic, 
I think Nov. '84) I described the following approach to
automatically accessing files from other user numbers:

The CP/M 2.2 BDOS can be modified to make specified files on
a drive "PUBlic".  PUBlic files are accessible from any user
number on the drive, and signified by the f2' bit (filename byte 2,
bit 7); they are read-write and can be used for virtual memory
(swap file) as well as loading COM, overlay, LIB, etc files from
another user number.

Subsequently, P2DOS, PZDOS and Z80DOS have incorporated this
PUBlic functionality.

PUBPATCH, a Z-80 patch for an *UNMODIFIED DRI CP/M 2.2 BDOS*
is listed in the article.  The files are available on simtel20.

--bridger