Beginning Assembly Troubles

In a computer architecture course that I'm taking, I have to write an x86 assembly program that displays information in the following format,where the first line is my own name, and the second line is the system date and time.
I've got everything working just fine until I try to display the day of the week. The program compiles just fine in NASM, but after displaying my name, the program stops. It seems to be calculating, but never gets anywhere.
Can anybody help me figure out what's wrong?

This is the assignment description.

This is my progress so far (ZIP file containing the .ASM file).

Is there any reason you couldn't have just posted your script in [ code ] tags?

I'm going to do that for you... I assume it's windows asm, although i don't know for sure.

Actually, LP, it's DOS assembly (it uses the DOS and BIOS interrupts), though it will run under Windows of course.

OK, a few things I've noticed offhand. First off, you don't actually need to include the exebin.mac file, as you don't seem to be using any macros. Mind you, it maybe that there are some macros you could use, but I'd need to see the macros your professor has set up to be sure. I assume it's something that your professor requires you to include, though.

Second, you are getting the day and date info, but then overwriting the date part when you load the address of the day string into DX (which keep in mind is general-purpose register D, full register). According to the interrupt list, the INT 0x21, function 0x2A DOS call (get system time) deposits the month into DH (General register D, high or upper half), and the day of the month into DL (General register D, lower half). You need to save those two values somewhere first, or else you'll lose them, and won't have the value later when you go to print the rest of the date. You haven't done that part of it yet, so it's not a big deal, but you'll need to have that for the final version later. I think that BH and BL should be free at this point; if not, you can use 'resb' ('reserve byte') to set aside some memory variables.

The main thing I see, though, is that you are letting the values fall through after it finds the correct value; that is to say,if it finds a value of zero, then it continues testing the results for all the others. You should have it jump to the end of the switch instead.

Finally, you don't have any sort of default or failure-mode handling; if a value is out of bounds, you have it jump back to the top without changing it, which would give an infinite loop. Since the value given by DOS shouldn't ever be above 6, this probably will never happen, but you might want to have a final 'dBad' case instead of jumping back to dSun just as a matter of sanity checking. This combined with the issue above may well be the source of the problem.

While testing the problem, you might want to start by trying to set it to print a fixed one of the strings, such as sunday. If that works, then the problem must be in the logic; otherwise, the problem is probably with the call to the DOS routine.

On a purely minor note, I might add that it would be slightly more efficient in terms of overall size (and avoid a trivial amount of redundancy) if you eliminated the spaces and the comma in the strings themselves, and printed it out separately. There would be a bit of extra overhead from the extra call, though. Which you do is a matter of personal coding aesthetics, really.

Also, I would have used a table lookup of some sort rather than a switch, but I don't know if your professor has covered enough that you would know how to do that yet; from the problem description, I gather that this is how he is expecting you to do this, so it's just as well.