nidud, thanks, though I cannot get it to work. I tried it, but now I get an output of 'á', which looks like it is ASCII character 160. If I change the .model to tiny, the output will be '0'. I'm not sure why the model affects the output.
My code is now:
.model small
.data
count1 db 4
.code
main proc
mov ax, SEG _DATA
mov ds, ax
mov dl, count1 ; Input character to dl
add dl, 48 ; add 48 to dl
mov ah, 2h ; Code for write character
int 21h ; Display character in dl
endp
end main