Matija:
 MT> I am writing a little operating, but i have a little problem. When i
 MT> try to execute this
        I did too, pretty cool looking core dump on my machine!
        First, change the end of string character to a 'NULL', ASCII
character 0.  Then you can use this routine as a general purpose string
output routine.  This is known as an ASCIIZ string:
        BootMsg db      'Loading OS...', 0
 MT> MsgLoop: MOV    DX,[SI]
        This line can confuse the assembler, but not yield an error.  Use
the explicit form:
      MsgLoop:  MOV     DL, byte ptr [SI]
        
        Then look for the end of the string:
 MT> CMP DX,'0'
                CMP     DL, 0
        Make sure that you can SEE the attribute
 MT> MOV    DH,7
                MOV     DH, 2
        Then continue to be explicit, with the added note that this will
write to the upper corner of the screen in CGA text modes only:
 MT> MOV    ES:[BX],DX
                MOV     word ptr ES:[BX], DX
        So the whole deal should look like:
        seg_a   segment byte    public
                assume  cs:seg_a; ds:seg_a
                org     100h
        main:   jmp     start
        b_msg   db      'Loading OS...', 0
        start:  mov     ax, 0B800h              ; Point to CGA screen
                mov     es, ax
                mov     si, offset b_msg        ; Point to b_msg string
                xor     bx, bx                  ; Clear BX
        msg_l:  mov     dl, byte ptr [si]       ; Get a character
                cmp     dl, 0                   ; See if it is NULL
                je      msg_e                   ; If it is, end
                mov     dh, 2                   ; I think green is cool
                mov     word ptr es:[bx], dx    ; Send the char/attr pair
                inc     si                      ; Increment the pointers
                inc     bx
                inc     bx
                jmp     msg_l                   ; Next character
        msg_e:  ret
        seg_a   ends
                end     main
        You could expand on this routine and offer users of the OS a
wide range of screen functions...  Sort of like DOS, but don't make them
so bad to use!  
        Ron Avery
... Real programmers confuse XMAS & Halloween: DEC 25=OCT 31!
--- Blue Wave v2.12 [NR]
---------------