Assembly language

Question

I am very much a rookie. I am sure this is very basic but I have gone over this a number of times. I am trying to get my program to display a string on two different lines. This is a .com program and I am using A86 compiler. This is for HW and i am not trying to cheat or anything like that because I really want to know what I am doing wrong.

jmp start               ; This will start the program

;============================

  msg   db  "Hello Word.$"      ; A string variable 
  msg   db  "Michael J. Crawley$"   ; A string variable with a value.

;============================

start:

  mov ah,09             ; subfunction 9 output a string

  mov dx,offset msg         ; DX for the string

  int 21h               ; Output the message

  int 21h               ; Output the message

exit:

  mov ah,4ch
  mov al,00             ; Exit code 

  int 21h               ; End program

Answer 1

Two definitions of msg?

Answer 2

Here are your specific problems:

• You define msg twice (a86 will barf on that).
• You call int21 fn9 with the same value of msg so you're not printing the two messages out, just two copies of the first.
• You don't have a newline character in either message so they'll abut each other rather than be on separate lines.

The solutions to those points (without providing the actual code).

• Label the second message as msg2.
• Load msg2 into dx before calling int21 for the second time.
• Change the messages to put a newline before the '$' symbol (or at least the first one).

---

Update: Since some other helpful soul has already provided source, here's my solution. I would suggest you learn from this and modify your own code to do a similar thing. If you copy it verbatim from a public site for classwork, you'll almost certainly be caught out for plagiarism:

         jmp start                   ; This will start the program

msg      db  "Hello Word.",0a,"$"    ; A string variable .
msg2     db  "Michael J. Crawley$"   ; A string variable with a value.

start:   mov ah,09                   ; subfunction 9 output a string
         mov dx,offset msg           ; DX for the string
         int 21h                     ; Output the message
         mov dx,offset msg2          ; DX for the string
         int 21h                     ; Output the message
exit:
         mov ah,4ch
         mov al,00                   ; Exit code 
         int 21h                     ; End program

This outputs:

Hello Word.
Michael J. Crawley

Answer 3

I'm not familiar with a86, but with NASM & MASM you need an "org 100h" assembler directive at the beginning of a com program. The way it is now, offset msg is 0x2, and that'll try to print from the second byte of the program segment prefix (a 16 bit word that holds the segment of the top of memory available to you).