Zhiyong Xu writes: > I knew if I put real number parameters, it will work fine. So you knew the answer already. > I just want to know if I did not put function prototype, how system > will deal with it, and why it generate this error. Because in the absence of a prototype, an int is passed to a function expecting a double. In the presence of a prototype, the ints are converted to doubles before being passed. > > But working without prototypes is stupid and > > pointless. Don't do it. Andrew.