Printing a new line in assembly language with MS-DOS int 21h system calls

Question

I've been trying to print a new line while also printing the alphabet using assembly language in nasmide for the past few days and can't get it, what I've tried so far has either printed nothing, printed just A or printed a multitude of symbols, Google hasn't been helpful to me so I decided to post here.

My code so far is

CR equ 0DH
LF equ 0AH

main:
mov AH,02H
mov CX,26
mov DL, 'A'

while1:
cmp DL, 'A'
add DL, 01H
int 21H
mov DL, 0DH
mov DL, 0AH
int 21H
cmp DL, 'Z'
je Next
jmp while1

Next:
mov AH,4CH
int 21h

Solution 1

Code for printing new line

MOV dl, 10
MOV ah, 02h
INT 21h
MOV dl, 13
MOV ah, 02h
INT 21h

ascii ---> 10 New Line

ascii ---> 13 Carriage Return

That is code in assembly for new line, code is inspirated with writing machine. Our professor told us the story but I'm not good at english.

Cheers :)

Solution 2

Well, first off:

mov DL, 0DH
mov DL, 0AH
int 21H

Isn't going to do you any good. You load 0Dh into DL and then immediately overwrite it with 0Ah without ever having used the first value... You need to make your call (int 21h) on BOTH characters...

Furthermore, you're using DL for newlines overwrites the prior use for the character... You need to save and restore that value as necessary.

Solution 3

100% works.

CR equ 0DH
LF equ 0AH

main: 
    mov DL, 'A'

while1:
    mov AH,02H      ;print character
    int 21H 

    mov BL, DL      ;store the value of DL before using DL for print new line

    mov DL, 10      ;printing new line
    mov AH, 02h
    int 21h
    mov DL, 13
    mov AH, 02h
    int 21h

    mov DL, BL      ;return the value to DL

    cmp DL, 'Z'
    je exit 
    add DL, 1       ;store in DL the next character
    jmp while1

exit:
    mov AH,4CH
    int 21h