ALP to change lowercase letter to UPPERCASE letter in 8086 microprocessor

.model small
.stack
.data
 name1 db 'word to change in uppercase$'
 .code
 main proc
 
 .startup
 
 mov dx,offset name1
 mov ah,09h
 int 21h 
 
 mov cx,18
 mov si, offset name1
UPPERCASE: 
 sub [si],20h ;note: to change UPPERCASE into lowercase add 20h
 mov dl,[si] 
 mov ah,02h
 int 21h
 inc si
 loop UPPERCASE
 
 .exit
 main endp
 end main