Print ASCII char and its corresponding hexadecimal code using multiple modules in x86 DOS ASM

Question

I have an assignment for tomorrow and I'm losing my mind I don't know how to do this. Basically I have to print all chars from position 32 to 127 and their respective code in hexadecimal format near them. Something like this:

[space char] 20h
! 21h
" 22h
etc

Until now I have only managed to do this: https://i.stack.imgur.com/UneFx.png

The thing is I don't know how to convert from a decimal value to a printable (so I have to print for example if I want to print the character '3' I would need to print the value 33h, etc.) hexadecimal value.

10l9.asm:

; 10. Print on the screen, for each number between 32 and 126, the value of the number (in base 16) and the character whose ASCII code the number is.

assume cs:code, ds:data

data segment public
nr db 32
hex db 20h
data ends

code segment public
extrn   tipar:proc
start:
mov ax, data
mov ds, ax

lea si, nr
cld
bucla:
    cmp nr, 127
    je final
    mov ah, 0
    mov al, nr
    mov bh, 0
    mov bl, hex
    call tipar
    inc nr
    inc hex
jmp bucla
final:
mov ax, 4C00h
int 21h
code ends
end start

print.asm:

    assume cs:code, ds:data
data segment public
    buffer dw 15 dup (?)
    tmp db 5 dup (?), 13, 10, '$'
data ends

code segment public
public tipar    ; the subprogram 'tipar' is made visible to other modules too
tipar:
; input: ax = the number that has to be printed on the screen
; the subprogram prints the number on the screen
; it does not modify the registers, except for ax

; we save the registers so that we can use them inside the subprogram
    push cx
    push dx
; we compute the representation on the number in base 10
    ;mov bx, offset tmp+5  ; bx=the address of the least written digit
    ;mov cx, 10 ; cx = 10 (constant)
    mov si, 0
    mov buffer[si], ax
    mov cx, 5
    spatiere:
        inc si
        mov buffer[si], 32
        loop spatiere       
    inc si
    mov bh, 0
    mov buffer[si], bx
    inc bx
    inc si
    mov buffer[si], 104
    inc si
    mov buffer[si], 13
    inc si
    mov buffer[si], 10
    inc si
    mov buffer[si], '$'

    mov dx, offset buffer
    mov ah, 09h
    int 21h

    pop dx
    pop cx
    ret

code ends
end

i've managed to do it (well partially) .. i'll post below how i did it in case someone has a similar problem:

mov bx, offset tmp+5
mov cx, 16
bucla:
    mov dx, 0
    div cx
    dec bx
    add dl, '0'
    mov byte ptr [bx], dl
    cmp ax, 0
    jne bucla

Based upon your output, you're obviously just reprinting the original character in place of its hex value. To print its hex value: (1) split it into two 4-bit pieces (hex digits), (2) convert each of the hex digits to ASCII (this can be done with a character table look-up or with a little code that checks if it's `0` to `9` add `20h` otherwise add `('A'-10h)`, and (3) print these two determined characters in order. You might want to make that its own little subroutine. — lurker, Jan 08 '14 at 14:14
http://stackoverflow.com/questions/3853730/printing-hexadecimal-digits-with-assembly — Ciro Santilli OurBigBook.com, Sep 21 '15 at 09:18

mirabilos · Accepted Answer · 2015-12-22T15:23:01.633

1

To convert a byte (in AL) to two bytes corresponding to the ASCII codes for the respective nibbles (in AX, little endian (high nibble in AL)), you can use this code (GNU as):

        .intel_syntax noprefix
        .code16
c2hex:
        mov     ah,al
        shr     al,4
        and     ah,0x0F
        add     ax,0x3030
        cmp     al,0x39
        jbe     1f
        add     al,7
1:      cmp     ah,0x39
        jbe     2f
        add     ah,7
2:      ret

The output is suitable for STOSWing into a string, for example.

Like numbers/digits, letters are sequential. The difference between 0x3A (0x30 + 10) and 'A' (0x41) just happens to be 7, which is where that number in the second-to-last line comes from. (The line two up, at the 1: label, checks for a letter.)

edited Dec 22 '15 at 15:23

answered Jan 08 '14 at 19:54

mirabilos

5,123
2
46
72

i did it by adding the value of the ascii '0' char (which is 30h) to every hexa char in order to obtain it's ascii equivalent.. and then i treated each case for letters (A, B, C, D, E, F) ..this seemed easier and more beginner-friendly for me – serge Jan 09 '14 at 10:14
when i have the time i'll try your method too – serge Jan 09 '14 at 10:15

Print ASCII char and its corresponding hexadecimal code using multiple modules in x86 DOS ASM

1 Answers1