Hi all, I've wrote this : a = pow(2,0); the result is a = 295 !!! b = pow(2,1); the result is 1. OK ! I've read at the following link : http://www.keil.com/support/docs/259.htm it says the math.h lib has a bug in C51 V5.10 I'm currently using C51 V5.50. Is this bug reported in this version ? If not, have you an idea of the problem ? Regards Stephane