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 Post subject: simplest possible design
PostPosted: Sat Oct 30, 2021 2:18 am 
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Joined: Fri Nov 17, 2006 5:26 am
Posts: 72
I have just completed proof of concept for PDOS-generic.

This uses an existing host system as a glorified BIOS, and
essentially exports the host C library so that the emulated
disks can be accessed using standard fopen/fseek/fread/etc.

The OS in turn exports an independent C library for use by
applications, which are subsequently tiny.

There is no emulator required, and the code runs at native
CPU speed. The disks are still emulated by host files though.

All code is portable C90 so you can take this MSDOS-like
environment to any alien environment.

I have Windows downloads available at the bottom of
http://pdos.org

The main source file is here:
https://sourceforge.net/p/pdos/gitcode/ ... ric/pdos.c

I'm interested in any technical analysis.

Thanks. Paul.


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 Post subject: Re: simplest possible design
PostPosted: Wed Dec 01, 2021 4:41 am 
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Location: Oscillating between two different potentials
I don't think I'm qualified for technical analysis, but from a user's perspective I always like operating systems which can run under another. They have the potential to let you use a consistent environment anywhere. As for this one, with no CD/CHDIR and DIR not accepting any arguments, I can see it's early days yet. Is PDOS on hardware this limited, or is this not the same command.com? I'm curious about the virtual files MINIHD B S and SYSTEM~1 (if that's what they are).

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 Post subject: Re: simplest possible design
PostPosted: Wed Dec 01, 2021 5:12 pm 
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eekee wrote:
I don't think I'm qualified for technical analysis, but from a user's perspective I always like operating systems which can run under another. They have the potential to let you use a consistent environment anywhere.

Yes, I'll be able to take all my tools with me too.

Quote:
As for this one, with no CD/CHDIR and DIR not accepting any arguments, I can see it's early days yet. Is PDOS on hardware this limited, or is this not the same command.com?

It's not the same as the one from PDOS/386. PDOS/386 has all of the above. I just need to bring that functionality across. It's not a straightforward copy though, so I'm still waiting to make sure the technical analysis is done before I begin that work. If you want to see what PDOS-generic will eventually look like, just run PDOS/386 instead.

Quote:
I'm curious about the virtual files MINIHD B S and SYSTEM~1 (if that's what they are).

The "dir" command is a crude listing of the directory. "MINIHD" is a volume label, and "SYSTEM~1" is the short name for "System Volume Information". It works properly in PDOS/386. Basically PDOS-generic is intended to be how PDOS/386 should have been written from the start, if I knew what I now (think I) know. I should have provided a "bios" layer to the real BIOS, for PDOS-generic. There has been a bit more technical analysis done in that I think the BIOS layer should use the mainframe flavor of PDPCLIB, which deals with "block" devices. But I'll need to restructure PDPCLIB because it's currently either block or character mode, whereas I believe I need both. And I also need to add ANSI escape sequence processing to PDPCLIB (my C library), for the BIOS layer to use, as it can't/shouldn't go into PDOS-generic.


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