i need to write a program that compute (a+b)/(c^2+d^2); if someone have lecture or can do for me .it will be gratefully

How much assembly do you already know? Its really probably not all that hard to do. You need to declare storage for four variables, a, b, c and d. First calcaulate c^2 (which is just c * c), and d^2 (d * d). store that result away somewhere. Then calculate a+b. Finally divide the result of a+b by the denominator previously calculated.

Will I write this for you? No. Its your homework, not mine.