Taradao

[ORG 0x100]

jmp @Principal

@WriteCh:

pusha
push es

mov dx, 0xB800            ;Video location
mov es, dx                ;es = dx
mov cx, ax                ;cx = ax (col, line)
mov al, 80                ;al = 80
mul ah                    ;multiply ah by al -> ah * 80
xor ax, ax                ;ax = 0
add al, cl                ;
adc ah, 0                 ;using this, it add cl to ax
shl ax, 1                 ;ax = ax * 2
mov di, ax                ;di = ax (di must be the position in the screen in dec)
mov ax, bx                ;ax = bx (colors and char)
stosw

pop es
popa
ret

@Principal:

mov al, 25                ;col
mov ah, 41                ;line
mov bh, 0x2F              ;foreground and background
mov bl, 'A'               ;char to print
call @WriteCh

@Fim:

mov ax, 0x4C00
int 0x21

;Formula -> 2*(lines*80+cols)