org 100h


jmp start



string db 20, 22 dup('?')
new_line db 0Dh,0Ah, '$'                ; print new line

start:


lea dx, string

mov ah, 0ah
int 21h

mov bx, dx
mov ah, 0
mov al, ds:[bx+1]
add bx, ax                              ; point to end of string.

mov byte ptr [bx+2], '$'

lea dx, new_line
mov ah, 09h
int 21h


lea bx, string

mov ch, 0
mov cl, [bx+1]                          ; get string size.

jcxz null                               ; is string is empty?

add bx, 2


upper_case:

                                         ; check if it's a lower case letter:
cmp byte ptr [bx], 'a'
jb ok
cmp byte ptr [bx], 'z'
ja ok

                                         ; convert to uppercase:

and byte ptr [bx], 11011111b

ok:
inc bx                                    ; next char.
loop upper_case



lea dx, string+2
mov ah, 09h
int 21h


mov ah, 0
int 16h


null:
ret