bogus

[ORG 0x100]

jmp @Principal

@WriteCh:

pusha
push es

mov dx, 0xB800
mov es, dx
mov cx, ax
mov al, 80
mul ah
push cx
movxz cx, cl
add ax, cl
pop cx
mov cx, ax
xor ax, ax
mov al, 2
mul cx
push bx
mov bx, ax
xor ax, ax
mov al, 2
mul bx
mov di, bx
xor bx, bx
pop bx
mov ah, bh
mov al, bl
stosw

pop es
popa
ret

@Principal:

mov al, 25                ;col
mov ah, 41                ;line
mov bh, 0x2F
mov bl, 'A'
call @WriteCh

@Fim:

mov ax, 0x4C00
int 0x21