; bai tap nhap vao mot chuoi roi chuyen ki tu hoa thanh thuong va nguoc lai
.model small
.stack 100h
.data
t db 'nhap vao mot chuoi',13,10,'$'
s db 99,?,100 dup (?)
.code
main proc

mov ax,@data
mov ds,ax

mov ah,09
mov dx,offset t
int 21h

mov ah,0ah
mov dx,offset s
int 21h

mov si,offset s+2
buoc3:
mov al,[si]

cmp al,0dh
je buoc10

cmp al,'a'
jb buoc7

cmp al,'z'
ja buoc7

sub al,20h
mov [si],al

jmp buoc9

buoc7:

cmp al,'A'
jb buoc9

cmp al,'Z'
ja buoc9

add al,20h
mov [si],al

jmp buoc9
buoc9:

inc si
jmp buoc3

buoc10:
mov al,'$'
mov [si],al

mov ah,02
mov dl,0dh
int 21h

mov ah,02
mov dl,0ah
int 21h

mov ah,09
mov dx,offset s+2
int 21h

mov ah,4ch
int 21h

main endp
end main