[bits 32]

VIDEO_MEM equ 0xb8000
WHITE_ON_BLACK equ 0x0f

;global data
STR_HEX_OUT_PM:
    db "0x0000",0

; print [ebx] at ecx
print_string_pm:
    pusha
    mov edx, VIDEO_MEM
    add edx,ecx
    print_string_pm_loop:
    mov al,[ebx]
    mov ah, WHITE_ON_BLACK
    cmp al,0
    je print_string_pm_done
    mov [edx],ax
    add ebx,1
    add edx,2
    jmp print_string_pm_loop

print_string_pm_done:
    popa
    ret

;print_hex_pm routine (dx) at ecx
;will print the value of the bx register as hex to the screen
print_hex_pm:

    pusha
   

    ;begin with last hex val (hex_out[5])
    mov bx,STR_HEX_OUT_PM+5

    ;lets loop throuth all 4 'digits'
    print_hex_pm_loop:

    ;get least significan hex digit to cx
    mov cx,dx
    and cx,0x000F

    ;check range (0-9 vs a-f)
    cmp cx,10
    jl print_hex_pm_setnum

    ;set hex a-f
    mov al,'A'-10		
    add al,cl
    jmp print_hex_pm_al

    ;set hex 0-9
    print_hex_pm_setnum:
    mov al,'0'		
    add al,cl

    ; set hex_out[bx] to al
    print_hex_pm_al:
    mov [bx],al

    ;proceed with the next significant hex 'digit'
    dec bx
    shr dx,4

    ;check if finished (otherwise loop)
    cmp bx,STR_HEX_OUT_PM+1
    jne print_hex_pm_loop

    ;output complete hex string and return to caller
    popa
    mov bx,STR_HEX_OUT_PM
    call print_string_pm
    ret