How do I generate a random number between 0 and x in windows?

rand() % x

rand() %(x+1), actually

He asked "between" not "inclusive":

rand() % 5 : 0 -> 4 // there are 5 numbers here
rand() % (5 + 1) : 0 -> 5 // there are 6 numbers here

Actually, use something like

( (float)rand() / (RAND_MAX + 1) ) * N

to generate # between 0-N

This would give a more distributed random number than the rand()%N

and this has to do with isometric, how...?