[Coco] Re: Floppy access from within XP

[John E. Malmberg]

Neil Morrison wrote:
> 
> But ISTR that this necessitated alteration of a table in RAM, and reversing
> the change afterwards. This is what most 'SuperDisk like' utilities do,
> AFAIK.

Well, the documented procedure was:

1. Make a BIOS call to indicate that you were changing the vector for 
your program.

2. Copy the existing table into local program RAM.

3. Change the vector to point to the new table.

On program exit, MS-DOS was supposed to clean everything up, but really 
a program should take care of these things.

 From DOS 3.x to about 5.x IIRC: the Undocumented DOS says that because 
the size of the table was changed with out being documented, such well 
written programs broke.

If the program was incorrectly written to modify the table directly, it 
continued to work.  Thus reinforcing bad programming habits.

-John
wb8tyw(at)qsl.network
Personal Opinion Only