How to print a string inside of a loop in assembly (MASM)

Question

So I'm new to assembly, and my professor is far from helpful when it comes to actually explaining what's happening.

In class, we set up loops like this:

mov si, 0
mov cx, 5 (repeating the loop 5 times)

L1:
   ...
   loop L1

And we print strings like this:

mov ah, 40h                 ;write to 
mov bx, handle              ;file
mov cx, lmess2              ;number of bytes to write
mov dx, offset mess2        ;
int 21h

So now the issue is that I need to print a string inside the loop. The issue I see with this is that the CX register is used in both the string printing and the loop, so when I try running it, it hangs, as expected.

Is there a different register/method I can use for the loop and the string printing?

Perhaps I can compare the value of the SI register to however many iterations of the loop I want, and then use a JE jump to jump out of the loop? But to me that seems a bit odd.

If anyone could guide me in the right direction, I'd greatly appreciate it. I'm sure there's an easy way to do this that I'm overlooking.

Answer 1

Two solutions :

SOLUTION #1

mov si, 0
mov bp, 5  ;DON'T USE CX, USE AN UNUSED REGISTER, LIKE BP.

L1:
   ...
   dec  bp      ;BP - 1. Zero-Flag turns on when BP becomes zero.
   jnz  L1      ;IF BP != 0 JUMP L1. JNZ = jump if last result is not zero.

SOLUTION #2

mov si, 0
mov cx, 5 (repeating the loop 5 times)

L1:
   PUSH CX         ;PRESERVE CX BEFORE IT CHANGES.
   ... ;PRINT HERE.
   POP  CX         ;RESTORE CX FOR PREVIOUS VALUE.
   loop L1

The chosen solution depends on the situation : using registers is the fastest way, pushing-popping is slower (because of stack). If you have unused registers, use them, it's faster, if you don't, use stack.