data segment
buf db 2
db ?
db 1 dup(0)
data ends
code segment
main proc far
assume cs:code,ds:data
start:
push ds
sub ax,ax
push ax
mov ax,data
mov ds,ax

flag1:
mov dx,offset buf
mov ah,10
int 21h
sub buf+2,30h
mov al,buf+2

cmp al,65
jz exit

cmp al,10
jns flag2

cmp al,1
js flag2
mov cl,al
mov ch,0
mov dl,1
again1:
push cx
mov cl,dl
push dx
add dl,30h
again2:
push dx
mov ah,2
int 21h
mov dl,' '
mov ah,2
int 21h
pop dx
loop again2
mov dl,13
mov ah,2
int 21h
mov dl,10
mov ah,2
int 21h
pop dx
inc dl
pop cx
loop again1

mov al,buf+2
dec al
cmp al,0
jz flag2
mov cl,al
mov ch,0
mov dl,al
again3:
push cx
mov cl,dl
push dx
add dl,30h
again4:
push dx
mov ah,2
int 21h
mov dl,' '
mov ah,2
int 21h
pop dx
loop again4
mov dl,13
mov ah,2
int 21h
mov dl,10
mov ah,2
int 21h
pop dx
dec dl
pop cx
loop again3
flag2:
jmp flag1

exit:
ret
main endp
code ends
end start