i want to check if either the "up" or "down" key has been pressed on the keyboard.

what i though it would be:

mov ah,01;get a keystroke
int 21
mov bh,al
cmp bh,50h
je up
cmp bh,48h
je down
jmp mainloop

don't know if 50 and 48 are the right numbers when comparing. do they have to be in hex? plz help!
what are the values for the up and down arrow key?