Getting an NTVDM error while adding '$' to array in TASM

Question

ideal
model small
stack 1024
dataseg
    array1 db 11 dup(?)
codeseg
org 100h
PROC MAIN
    CALL GETINPUT
    CALL PRINTARRAY
EXIT:
    mov ah, 4ch
    int 21h
ENDP

PROC PRINTARRAY
    lea dx, [array1]
    mov ah, 9
    int 21h
    ret
ENDP

PROC GETINPUT
    mov bx, offset array1
    GET:
        CALL GETCHAR
        cmp al, '.'
        je ENDGET
        mov [array1+bx], al
        inc bx
        cmp bx, 10
        jge ENDGET
        CALL PRINTSPACE
        jmp GET
    ENDGET:
    mov [array1+bx], '$'
    ret
ENDP

PROC GETCHAR
    mov ah, 1
    int 21h
    ret
ENDP

PROC PRINTSPACE
    mov dl, ' '
    mov ah, 2
    int 21h
    ret
ENDP

PROC PRINTCHAR
    mov ah, 2
    int 21h
    ret
ENDP

END MAIN

Im getting an NTVDM error cs:0423 ip:0125 when adding '$'. without the sentinel i can't print the array without garbage and other characters in it. :( i dont know if its because of my OS, windows 7 32bit, or assembler. please help me. :(

Your loop appears to allow up to 10 chars to be stored in `array1` (your exit condition is `al=='.' || bx >= 10`. So you might end up writing the '$' to `[array1+10]` (i.e. the 11th byte), which is out of bounds since you've declared array1 as an array of 10 bytes. — Michael, Mar 06 '13 at 14:38

score 1 · Answer 1 · answered Mar 06 '13 at 14:05

1

Look at these two instructions:

mov bx, offset array1
GET:
    ...
    mov [array1+bx], al

Doesn't it look odd to you that you take the address of array1 and then add it to itself in array1+bx?

answered Mar 06 '13 at 14:05

Alexey Frunze

61,140
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180

Yeah. I get your point. Tried changing it to 0 but still the error's still there whenever i add '$' – bheek Mar 06 '13 at 14:11
That's one of the problem. It works in debug but not in the terminal. – bheek Mar 06 '13 at 14:32
Did you change both instances where you write to the array? I.e. both inside the loop and after the loop? – Michael Mar 06 '13 at 14:35
Perhaps you need to do something about `cmp bx, 10 + jge ENDGET`? – Alexey Frunze Mar 06 '13 at 14:51
1

If you need to output 10 characters, then your buffer has to be 11 characters long to accommodate the `$` that you're adding. So `array1 db 11 dup(?)`. – Jim Mischel Mar 06 '13 at 14:55

Getting an NTVDM error while adding '$' to array in TASM

1 Answers1