Question

Trying to print a caracter

Asked by: tirengarfio1

Hi,

at first, the code i attach prints a "$" symbol. Then, when i push the up arrow key it should print another "$" above the first one, but it prints TWO. Why?

My other problem: I would like it only prints the "$" when i press the up arrow key (now it prints "$" for any key i press).

Assembly 8086

Bye

DOSSEG
	.MODEL SMALL
	.STACK 100h
	.DATA
 
 
	.CODE
 
 
INICIO:
 
	mov ax, @data
	mov ds, ax
 
 
 
	mov ax,03h 	; Peticion para limpiar pantalla
	int 10h
 
	;funcion de la interrupcion que nos permite posicionarnos
	mov ah,02h 	; colocar el cursor en una posicion definida
	mov dh,0Ah 	; fila
	mov dl,026h 	; columna
	
	int 10h 	; interrupcion de video
 
 
	mov dl, 024h	; Escribo el caracter "$"
	mov ah, 06h
	int 21h
 
bucle:
 
	mov ah, 08h	; Leo un caracter del teclado sin reproducirlo en la pantalla.
	int 21h
 
 
	cmp al, 18h	; Compruebo si el caracter pulsado es la flecha hacia arriba.
	je arriba
 
 
arriba: 
 
	
	
	mov ah, 02h	; Colocar el cursor en una posicion definida
	sub dh, 1	
	mov dl, 026h 	; columna
	mov bh,0 	; pagina de video activa generalmente la cero	
	int 10h
 
 
	mov dl, 024h
	mov ah, 06h
	int 21h
 
 
jmp bucle
 
 
FIN:
 
	mov ah, 4ch
	int 21h
	end INICIO

                                  
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Asked On
2008-03-15 at 13:45:50ID23244411
Tags

8086 assembly

Topic

Assembly Programming Language

Participating Experts
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Points
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Comments
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Answers

 

by: Infinity08Posted on 2008-03-16 at 02:21:04ID: 21136248

>> Then, when i push the up arrow key it should print another "$" above the first one, but it prints TWO.

Do you mean two $'s next to each other, or above each other ?


>> My other problem: I would like it only prints the "$" when i press the up arrow key (now it prints "$" for any key i press).

This part :

                cmp al, 18h     ; Compruebo si el caracter pulsado es la flecha hacia arriba.
                je arriba
         
        arriba:

So, you jump to arriba if you find a certain character, but if the character is different, you still continue at the arriba position. You need to add a bit of extra code :

                cmp al, 18h     ; Compruebo si el caracter pulsado es la flecha hacia arriba.
                je arriba
                ; <--- code to handle other key goes here
                jmp bucle        ; go to the beginning of the loop again
         
        arriba:


Btw, why don't you read the next character at the beginning of the loop ?

        mov dl, 024h
        mov ah, 06h
        int 21h

 

by: tirengarfio1Posted on 2008-03-16 at 06:14:29ID: 21136787

Hi infinity08,

>> Do you mean two $'s next to each other, or above each other ?

I meant two $'s one above each other.

Anyway, I attach my new code with your advises but now it only writes a $ above the first one when i push the up arrow key or the down arroy key. And when it writes that second $ it doesn't write any more $'s when i press again the arrow keys.



DOSSEG
	.MODEL SMALL
	.STACK 100h
	.DATA
 
 
	.CODE
 
 
INICIO:
 
	mov ax, @data
	mov ds, ax
 
 
 
	mov ax,03h 	; Peticion para limpiar pantalla
	int 10h
 
	;funcion de la interrupcion que nos permite posicionarnos
	mov ah,02h 	; colocar el cursor en una posicion definida
	mov dh,0Ah 	; fila
	mov dl,026h 	; columna
	
	int 10h 	; interrupcion de video
 
 
	mov dl, 024h	; Escribo el caracter "$"
	mov ah, 06h
	int 21h
 
bucle:
 
	mov ah, 08h	; Leo un caracter del teclado sin reproducirlo en la pantalla.
	int 21h
 
 
	cmp al, 18h	; Compruebo si el caracter pulsado es la flecha hacia arriba.
	je arriba
 
	cmp al, 19h	; Compruebo si el caracter pulsado es la flecha hacia abajo.
	je abajo
 
	
 
arriba: 
 
	
	
	mov ah, 02h	; Colocar el cursor en una posicion definida
	sub dh, 1	
	mov dl, 026h 	; columna
	mov bh,0 	; pagina de video activa generalmente la cero	
	int 10h
 
 
	mov dl, 024h
	mov ah, 06h
	int 21h
 
abajo:
 
	mov ah, 02h	; Colocar el cursor en una posicion definida
	add dh, 1	
	mov dl, 026h 	; columna
	mov bh,0 	; pagina de video activa generalmente la cero	
	int 10h
 
 
	mov dl, 024h
	mov ah, 06h
	int 21h
 
 
	jmp bucle
 
 
 
 
FIN:
 
	mov ah, 4ch
	int 21h
	end INICIO

                                              
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by: Infinity08Posted on 2008-03-16 at 06:21:47ID: 21136807

You probably want another

        jmp bucle

at the end of the arriba section (just before the abajo label).


Also :

        cmp al, 18h     ; Compruebo si el caracter pulsado es la flecha hacia arriba.
        je arriba
 
        cmp al, 19h     ; Compruebo si el caracter pulsado es la flecha hacia abajo.
        je abajo

If it's neither of those keys, it defaults to the arriba section. You want to place another jmp to the beginning of the loop right after the "je abajo".

You need to cover all flows ;)


Btw, I mistyped earlier : "Btw, why don't you read the next character at the beginning of the loop ?" <-- read should have been write. Right now, you have 3 times this same code :

        mov dl, 024h
        mov ah, 06h
        int 21h

If you put it once at the beginning of the bucle loop ... it should be fine :)

 

by: tirengarfio1Posted on 2008-03-16 at 07:37:17ID: 21137029

Hi again,

the code i attach this time I think it has your advices.

It works, but i have still the problem about the two $'s.

The sequence is this:

- The first $ is writen.
- I press the up arrow key.
- It writes a $ above the first. OK.
- I press the up arrow key again.
- The cursor goes above the second $, but it doesnt write anything.
- I press the up arrow key again and this time it writes 2 $'s above the the second $ (so i have totally 4 $'s)



DOSSEG
	.MODEL SMALL
	.STACK 100h
	.DATA
 
 
	.CODE
 
 
INICIO:
 
	mov ax, @data
	mov ds, ax
 
 
 
	mov ax,03h 	; Peticion para limpiar pantalla
	int 10h
 
	;funcion de la interrupcion que nos permite posicionarnos
	mov ah,02h 	; colocar el cursor en una posicion definida
	mov dh,0Ah 	; fila
	mov dl,026h 	; columna
	
	int 10h 	; interrupcion de video
 
 
 
 
bucle:
 
 
	mov dl, 024h	; Escribo el caracter "$"
	mov ah, 06h
	int 21h
 
 
	mov ah, 08h	; Leo un caracter del teclado sin reproducirlo en la pantalla.
	int 21h
 
 
	cmp al, 069h	; Compruebo si el caracter pulsado es la flecha hacia arriba.
	je arriba
 
	cmp al, 06Bh	; Compruebo si el caracter pulsado es la flecha hacia abajo.
	je abajo
 
 
	jmp bucle
 
 
arriba: 
 
	
	
	mov ah, 02h	; Colocar el cursor en una posicion definida
	sub dh, 1	
	mov dl, 026h 	; columna
	mov bh,0 	; pagina de video activa generalmente la cero	
	int 10h
 
 
	jmp bucle
 
abajo:
 
	mov ah, 02h	; Colocar el cursor en una posicion definida
	add dh, 1	
	mov dl, 026h 	; columna
	mov bh,0 	; pagina de video activa generalmente la cero	
	int 10h
 
 
	jmp bucle
 
 
 
 
FIN:
 
	mov ah, 4ch
	int 21h
	end INICIO

                                              
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by: Infinity08Posted on 2008-03-16 at 07:45:53ID: 21137054

>> the code i attach this time I think it has your advices.

Indeed ;)


First of all, one optimization :

        bucle:

                mov dl, 024h    ; Escribo el caracter "$"
                mov ah, 06h
                int 21h

        bucle2:                     ; <---- add this

                mov ah, 08h     ; Leo un caracter del teclado sin reproducirlo en la pantalla.
                int 21h
 
                cmp al, 069h    ; Compruebo si el caracter pulsado es la flecha hacia arriba.
                je arriba
 
                cmp al, 06Bh    ; Compruebo si el caracter pulsado es la flecha hacia abajo.
                je abajo
 
                jmp bucle2       ; <---- modify this jmp

Just to avoid writing a $ that is already there ;)



>> It works, but i have still the problem about the two $'s.

I'm thinking about this one ... Does it happen consistently (ie. do you always get the same result) ?

 

by: tirengarfio1Posted on 2008-03-16 at 09:35:26ID: 21137389

>> I'm thinking about this one ... Does it happen consistently (ie. do you always get the same result) ?

Always happen the steps i wrote before.

 

by: Infinity08Posted on 2008-03-16 at 15:49:48ID: 21138887

>> Always happen the steps i wrote before.

I don't have an explanation for that, but here's something to try : instead of using dh to keep the row, store the row information somewhere else, and copy it into dh just prior to outputting the $. (it could be that some other operation manipulates the dh register)

If that doesn't help, it might be an I/O buffering issue ... but I'm not sure.

20120131-EE-VQP-002

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