DOS ain't dead - MS-DOS v7.10 disk sector access function 7305h: Error code?

ecm

Düsseldorf, Germany,
05.12.2025, 18:38

MS-DOS v7.10 disk sector access function 7305h: Error code? (Developers)

The interrupt list doesn't specify what error codes can be returned by int 21h function 7305h, just stating:

> Return: CF clear if successful
> CF set on error
> AX = error code

Trying to access an invalid sector as in l 100 A: 1000000 1 or trying to read from a dosemu2 mfs-redirected drive like l 100 C: 0 1 using my debugger results in a return with CY, ax=020Ch.

That doesn't seem to match any error codes known to DOS for normal int 21h functions. But it does seem like what int 25h returns in ah and al. So apparently this function returns errors in the int 25h/26h style?

The interrupt list should specify this.

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l

tkchia

13.01.2026, 16:57

@ ecm

MS-DOS v7.10 disk sector access function 7305h: Error code?

Post reply

Hello ecm,

> That doesn't seem to match any error codes known to DOS for normal int 21h functions. But it does seem like what int 25h returns in ah and al. So apparently this function returns errors in the int 25h/26h style?
> The interrupt list should specify this.

Well... unfortunately I think we are still not sure if the upstream Interrupt List project accepts updates. :-| It will indeed be nice if it does.

Thank you!

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https://codeberg.org/tkchia · https://gitlab.com/tkchia · 😴 "MOV AX,0D500H+CMOS_REG_D+NMI"

ecm

Düsseldorf, Germany,
13.01.2026, 19:26

@ tkchia

Interrupt List updates

Post reply

> > So apparently this function returns errors in
> > the int 25h/26h style?
> > The interrupt list should specify this.
>
> Well... unfortunately I think
> we are
> still not sure

Nitpick: You should use a [ msg= ] tag for the link to a different message in this forum, eg this one.

> if the
> upstream Interrupt List
> project accepts updates. :-| It will indeed be nice if it does.
>
> Thank you!

I won't hold my breath. I did hear about someone else wanting to eventually update the list though. That seems more likely to come to fruition.

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l

tkchia

22.01.2026, 17:04

@ ecm

Interrupt List updates

Post reply

Hello ecm,

> Nitpick: You should use a [ msg= ] tag for the link to a different message in this forum, eg this one.
Thanks for the tip. :-)

> I won't hold my breath. I did hear about someone else wanting to eventually update the list though. That seems more likely to come to fruition.
Interesting... I should check out this project and see what I might be able to do with it.

Thank you!

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https://codeberg.org/tkchia · https://gitlab.com/tkchia · 😴 "MOV AX,0D500H+CMOS_REG_D+NMI"