Printing array — getting strange output (emu8086)

问题

My question is related to printing an array in assembly 8086 language. I use 'emu8086' program.

The following piece seems fine to me (I'm a beginner), yet the result I get is: *P000, instead of: 12345.

  Main:

A DB 1,2,3,4,5 //my array

SUB SI, SI    //SI stands for counter and index here
LEA BX, A  

loop3:
MOV DX, [BX + SI] 

ADD DX, 30h //converting digit into character
MOV Ah, 2h
int 21h    //displaying the character in console window

INC SI
CMP SI, 5
JNE loop3             

end Main

Can you, please, explain what's wrong with my function ? Thank you in advance !

回答1:

The program, in the question, is incomplete. There are two vital lines missing:

    MOV AX, @DATA
    MOV DS, AX

Here I found the purpose of these.

Below are listed the things that made me change the program.

I found a good assembly program on this topic, based on which, step by step, I could analyze each line of code, and understand the meaning. I think this program explains everything.

There are some things I discovered:

Assembly language program should have a structure
Each register has its own purpose

So my program now looks this way:

    .MODEL SMALL
    .STACK 100H

    .DATA
    A DW 1, 2, 3, 4 ; it's my array

    .CODE   

    MAIN PROC

        MOV AX, @DATA
        MOV DS, AX


        LEA SI, A   ;set SI as offset address of A (of my array)
        MOV BX, 4   ;store the number of digits in BX register
        MOV CX, BX  ;CX is used as a loop counter

        LOOP1:

            MOV DX, [SI] ; Line 1
            ADD DX, 30h  ;convert digit to char and store in DX

            ;Print character stored in DX 
            MOV AH, 2h
            INT 21h

            ;Store in DX the ASCII code for 'space' character 
            MOV DX, 20h
            ;Print ' ' = space 
            INT 21h 


            ADD SI, 2 ;SI = SI + 2

        LOOP LOOP1 ; jump to label 'LOOP1' while CX != 0

    MAIN ENDP

The meaning for Line 1 I found here.
Here I found what instructions to use for printing characters, with all the explanations.
The ASCII Table was helpful.
About LOOP instruction.

回答2:

You'll want to verify that the DS register is loaded with the proper value, or your memory reads will be from the wrong segment.

回答3:

.MODEL SMALL
.DATA

    ARRAY DW 1,2,3,4,5
.CODE
.STARTUP

  MOV CX,5      

 MOV SI,OFFSET ARRAY

LOP:
    MOV DX,[SI]  
    ADD DX,30H

    MOV AH,2H
    INT 21H  

    INC SI 
    INC SI

LOOP LOP
.EXIT
END

TRY THIS

来源：https://stackoverflow.com/questions/35709437/printing-array-getting-strange-output-emu8086

标签

assembly

emu8086