例7.4

#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);
}