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mathassemblymasm32operationsq

Arithmetic operations in ASM Language

I just need some help. I don't fully understand and I am fairly new to masm32 so if you could explain, that would be great!

MOV AX, 200
ADD AX, 300
MOV RESULT, AX

Will result be equal to 500? I tried adding 3 and 2 and using this to show output:

MOV DX, RESULT
ADD RESULT, '0'
MOV AH, 02H
INT 21H

But the output is a candy cane character! Where is it wrong?

Now I assume subtraction will work the same as addition, so on to Multiplication we go. This is what I did for multiplication

MOV AX, 30
MOV BX, 8
MUL BX
MOV RESULT, AX

Is RESULT's value equal to 240?.... I tried AX as 3 and BX as 2. The output is a spade. Can you point me to the right direction?

Now division. 

MOV AX, 30
MOV BX, 12
DIV BX
MOV RESULT, AX

What holds the quotient? If what I read was correct, that would be AX, and DX holds the remainder...?

I have already done 8 bit arithmetic (using AL, BL, DL...) and I tried to apply it here, sadly, when the RESULT becomes greater than 128, it just outputs garbage. Someone suggested that I should declare my variables as 'RESULT dw ?' instead of 'RESULT db ?' and instead of AL BL registers I should use AX BX.... Now I'm stuck.

Any help would be appreciated! Sorry if these questions seem too trivial. Anyway, thanks in advance! :DD

Solution

  • MOV AX, 200
    ADD AX, 300
    MOV RESULT, AX
    Will result be equal to 500?

    Yes.

    I tried adding 3 and 2 and using this to show output:
    MOV DX, RESULT
    ADD RESULT, '0'
    MOV AH, 02H
    INT 21H
    But the output is a candy cane character! Where is it wrong?

    You're adding '0' to RESULT after moving RESULT to DX. You should probably add '0' to DL instead of to RESULT.

    Now division.
    MOV AX, 30
    MOV BX, 12
    DIV BX
    MOV RESULT, AX
    What holds the quotient? If what I read was correct, that would be AX, and DX holds the remainder...?

    DIV BX divides the 32-bit value DX:AX by BX, so you should clear DX before the division. The quotient will end up in AX and the remainder in DX.

    Someone suggested that I should declare my variables as RESULT dw ?

    If you're going to move 16-bit values to/from the variable (e.g. MOV RESULT,AX) then you should make the variable (at least) 16 bits.