http://www.arl.wustl.edu/~lockwood/class/cs306/books/artofasm/Chapter_6/CH06-2.html#HEADING2-451


The div instruction computes an unsigned division. 
If the operand is an eight bit operand, div divides the ax register by the 
operand leaving the quotient in al and the remainder (modulo) in ah. 

If the operand is a 16 bit quantity, then the div instruction divides the 32 bit quantity
in dx:ax by the operand leaving the quotient in ax and the remainder in [dx].