use:
inc di
not
inc dx

or you could use:
mov es:[di],ax
and do both bytes at once

Well, among other things, I don't understand what you're incrementing dx for. That's probably your problem right there—your attribute is overwriting your character, and the attribute never even gets set. You haven't said which assembler this is for, but I'm assuming that it's something like TASM.

Something that's sometimes a problem is that you're assuming that page 0 is visible when it's actually not. I'd suggest setting the page explicitly, just in case:

mov  ax, 500hint  10h 

Otherwise, you could ask the BIOS which page is currently visible and calculate the offset accordingly.

Now, I'm just going to run through approximately how I'd do it, just as an excersize for thinking (of course, there are tons of "right" ways to do it):

We need to make sure that we have the segment and offset of the screen buffer (we'll assume the origin at the moment) in the right registers for stosw (which we'll use later):

mov  es, 0b800hmov  edi, 0 

Then we have to set up the character and the attribute in the right register (ax) for stosw:

mov  al, 'A'mov  ah, 4 

Finally, we write the character to the buffer (using a string instruction for just one character seems silly, but it's easier to use and will be good when we display things in a loop):

stosw 

Needless to say, if you're trying to use 32-bit code, then this won't work because we'll have to have set up a descriptor table entry for the video buffer and have a selector to it. Otherwise, I think that what I showed should work just fine.


[edited by - merlin9x9 on October 7, 2003 9:44:49 PM]

Yes, it''s linear.

That sounds suspiciously like a page issue.