Question

I have a homework assignment to make a simple program in assembly language for the 8086 family of processors that reads and prints the total occupied space on a floppy.

Now I have several problems. I know I have to use interrupts but I have no idea which one and how it works, I tried Norton Guide but I didn’t find what I was looking for. Another problem is that I do not own a floppy or have a machine that has a floppy … well I have absolutely no way to test this program.

In other words I’m stuck

EDIT:

Also how do I multiply 3 Words ? Ax * Cx * Dx ? because Word * Word = Double Word … and I have no idea how to multiply Double Word with Word.

Answer 1

Your question is a little vague on this, but it sounds like you’re coding against the MS-DOS INT21 API.

If that’s the case, you’re looking for two commands:

• 1Ch (Get Allocation Information for Specific Drive) — if you multiply together AL, CX and DX, you’ll get the size of the disk in bytes.
• 36h (Get Free Disk Space).

The difference between the total size and the free space will give the occupied space.