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HOW TO DO DIRECT DISK IO FROM MSDOS UNDER WINDOWS?

Posted on 2003-03-19
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Last Modified: 2010-04-16
I wannted to write a program that can sort the FAT-TABLE of a FAT32-Drive
and it has to run from MSDOS under Windows!
Something that Windows isn't blocking away!
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Question by:Okey
5 Comments
 
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Expert Comment

by:VGR
ID: 8170532
please note that if you "run it from "DOS" under windows", you're not on true DOS and will be "blocked" whatever you try. You need to run it from TRUE DOS, ie having booted on a floppy.
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Expert Comment

by:mlmcc
ID: 8171178
Can MS-DOS work with FAT32?

mlmcc
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Expert Comment

by:VGR
ID: 8172159
yes I think. Starting with Win98SE "DOS"

see "boot floppy disk image Win 98" in google
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Author Comment

by:Okey
ID: 8173048
You seemed to be right VGR,
but isn't there a possibility
for example in protected mode
with which you can bypass or using Windows?
I thought about direct port access,
something working like Int 25&26
or DOS-Win95 API on INT21 AX=??4? CX=FFFFH.

I thought about to do simply,
what has been done under True DOS
to do under windows.

I don't know what Windows is doing to prevent this,
but it seems that,
the ports are simulated.

But how can this be?
I thought if i do direect access to the hardware
(communication with Drive-Processor)
that it would run,
because I thought that direct Hardware access under
DOS-Shell-Mode is possible.

Am I so wrong?

Please,
can someone explain,
how the hardware access is handled for DOS by Windows?

I think here are possibilities hidden.

Maybe someone knows a code solution,
that implements easily a protected mode routine,
that is accessing the nescesary WIN-API's for?

But at least,
I'm searching for something
like a direct Hardware access to a Harddrive
preferably from Realmode,
but protected mode would be OK, too.

I mean DOS Shell can't be emulating all the Hardware,
and I know that the DOS-Shell is working over the protected mode with windows,
especially for IRQ's like INT9 Keyboard Interrupt and so on.
So shouldn't there be a possibility
at least from protected mode?
Maybe implementing WIN-API's over protected mode?

The desired destination language is Turbo Pascal 7.0 and assembly.

Please,
I need a real experts comment for!
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LVL 50

Accepted Solution

by:
dbrunton earned 100 total points
ID: 8176225
>>> because I thought that direct Hardware access under DOS-Shell-Mode is possible.

The lock command is stopping you.  You have to enable or disable it to permit direct access.

Try lock at the command prompt under the dos window.

You may have to

swapvectors
exec(lock)
swapvectors

to get this to work for you.  Be very careful.
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