Hi. About 30 years ago, someone made a comment
on a group saying "until DOS is made 32-bit, DOS
extenders are just a kludge".
I didn't know much about DOS-specifics back then
to even understand the comment.
Microsoft abandoned the MSDOS API, but what
would a 32-bit version of the MSDOS API look
like if they hadn't abandoned it?
Since 1994, off and on, I have been working on
PDOS/386, which is designed to be a 32-bit
version of MSDOS/Freedos.
I have recently just completed relocation of OS
and app so that they can both run in a flat address
space, meaning that applications can directly
manipulate the hardware, e.g. by going
*(char *)0xb8000 = 'X';
With that change now in place, it is working to
my satisfaction technically (I want to return to
the days when blindingly fast applications could
be written by manipulating the hardware), and
I would like to solidify the API. What would a
32-bit MSDOS API ideally look like? My current
thinking is that both int86() and some wrapper
functions should be made available, which I
have already done here:
https://sourceforge.net/p/pdos/gitcode/ci/master/tree/src/pos.h
Note that this is all working, but I am interested
in tweaking the design/interface before lots of
16-bit MSDOS programs get ported to 32-bit, so
I am open to suggestions. E.g. I was thinking
that the PosAllocMem() should instead be put
on a different AH code and take extra parameters,
mainly a "location" which can be set to 20 to
request memory in the first 1 MiB, or 32 for the
full 4 GiB space, and in the future support 64.
PDOS/386 is explicit public domain (no license)
and written mostly in C, with a bit of assembler.
The way it works is that the OS and apps are
pure 32-bit protected mode, but when a service
like reading from disk is required, it converts the
protected mode BIOS interrupt into a real mode
interrupt. This conversion to real mode is
transparent to the OS and apps.
As a test, I tried porting micro-emacs from 16-bit
DOS to 32-bit DOS, and very few changes were
required. He was previously writing to the screen
buffer at 0xb8000 using an "int *" and I needed
to change that to "short *". I was thinking that
all the Freedos utilities could be similarly ported
so that I don't need to rewrite everything.
I don't need any code written. I just need peer
review of the design/API. Hopefully someone
can offer some opinions.
Thanks. Paul.
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