If MSDOS/PCDOS had been ported to the mainframe
(or any other CPU - even the 80386), something would
have had to be changed, as you can't do an 8086 INT 21H
to request DOS services.
With that in mind, z/PDOS-generic is my rendition, which
I have previously announced.
This time, it can run under MVS:
COPY INDD=((I1,R)),OUTDD=I2
IEB167I FOLLOWING MEMBER(S) LOADED FROM INPUT DATA SET REFERENCED BY I1
-
IEB154I BIOS HAS BEEN SUCCESSFULLY LOADED
IEB144I THERE ARE 0000287 UNUSED TRACKS IN OUTPUT DATA SET REFERENCED BY I2
IEB149I THERE ARE 0000019 UNUSED DIRECTORY BLOCKS IN OUTPUT DIRECTORY
IEB147I END OF JOB -00 WAS HIGHEST SEVERITY CODE
^Lcopying from file dd:in, mode binary
to file dd:out, mode binary
9564 bytes copied
^Lcopying from file dd:in, mode text
to file dd:out, mode text
123 bytes copied
^L
bios starting
enter command, exit to exit
about to execute program with entry point 02019408
welcome to PDOS-generic
running as dd:pdos
before printing parm
argv1 is -c
about to open disk
done open
lba is 1f8
fat type is
opening dd:config
shell name is :dd:pcomm
about to call app at address 024DF8B0
welcome to pcomm
type help for help
enter a command
d
a
t
e
Tue Aug 5 19:06:58 2025
enter a command
d
i
r
PDOS
TEST TXT
COMMAND EXE
CONFIG SYS
ád
DEVEL
BIOS EXE
PDOS EXE
TEST2 TXT
XXX TXT
TEST C
TEST S
át
TEMP ZIP
DOS
To some extent it is "proof of concept", but we have a
competent engineer (Dat Nguyen) from Vietnam who
is expected to refine this in due course.
There was one issue, which Dat has been working on
for months (a large part of which was training).
https://sourceforge.net/p/pdos/gitcode/ci/master/tree/pdpclib/stdio.c#l1743
/* this done_first variable is a workaround for what is presumed
to be a bug in mvssupa.asm
The first time a write is done, the read buffer should be
overwritten from the beginning.
But all subsequent writes require the first 4 bytes to be
skipped. We need someone to look at the mvssupa.asm.
Gerhard Postpischil wrote the relevant mvssupa.asm code,
but he died years ago
*/
Is anyone interested in looking at the S/370 assembler here:
https://sourceforge.net/p/pdos/gitcode/ci/master/tree/pdpclib/mvssupa.asm
You can obtain z/OS PCDOS from https://pdos.org
(second occurrence of PCDOS)
There is expected to be a z/OS Windows in due course, that
allows you to write minimal programs using msvcrt.dll. I have
already demonstrated that on the 68000.
Another development since the zpg announcement is that
z/PDOS-generic can now (effectively) drive a PC serial port
so it can run a BBS (pdpbbs.exe) or dial one (devil.exe).
Since it runs under an emulator, it is down to what the
emulator can provide. In my case, that is mfemul.exe, and
that runs under Windows, which means the mainframe can
run the BBS under real Windows.
I also produce a Windows mini-clone, which uses UEFI, and
I have asked Dat to work on enabling serial port there too,
which would in turn allow Virtualbox on a Mac M1 to run a
mainframe BBS. Since the mainframe is being emulated
either way, you can run it on a Mac.
Note that with a second OSA/ICC tunneling through a
Windows/Linux box with a real RS232 port, you should
be able to attach a real traditional modem to a mainframe,
depending on the definition of "attach".
Also note that I have only demonstrated z/OS PCDOS running
in batch, but it should run under TSO too.
If you had a 3270 emulator that was able to switch to an
EBCDIC version of ANSI X3.64, you should be able to run
microemacs under TSO this way. There should probably
be some standard way of the software signaling to the
terminal emulator that it is switching between 3270 and
EBCDIC ANSI.
One other plan afoot (the groundwork has already been
prepared) is to create an EBCDIC version of x86
Windows. This should allow certain mainframe data (that
behaves using the PDPCLIB rules) to be offloaded to
a PC and then certain C90 applications could do things
like quickly searching a large file, not under emulation,
and offloading work from the mainframe.
Another thing is that you can produce ASCII Windows
executables from the mainframe, as gccwin now works
there. You can produce EBCDIC Windows executables
too, but I haven't yet published an OS to run them.
That's all I can think of at the moment.
BFN. Paul.
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