我这是看谭浩强的范例，输入结果后输出的竟然这样的：
please enter a and b:3.4，5.6
sum is -107374172.600000
Press any key to continue



这是我的程序，求大神看看这什么问题？
#include<stdio.h>
int main()
{float add(float x,float y);
float a,b,c;
printf("please enter a and b:");
scanf("%f,%f",&a,&b);
c=add(a,b);
printf("sum is %f\n",c);
return 0;
}                                                                                                                                                                                                                                                                                                                                                                                                                              

float add(float x,float y)
{float z;
z=x+y;
return(z);
}

多谢，还真是我在输入时无意间用的是汉语的逗号，导致结果不正确！