C Program to find average of 2 numbers using function

/* 
C  program computes the average of two values.
*/

#include<stdio.h>

double average(double, double) ;


int main() {
   double outerDiameter, innerDiameter ;
   double avgDiameter ;

   printf("Outer Diameter = ") ;
   scanf("%lf", &outerDiameter) ;

   printf("Inner Diameter = ") ;
   scanf("%lf", &innerDiameter) ;

   avgDiameter = average(innerDiameter, outerDiameter) ;

   printf("Average = %f\n", avgDiameter) ;
   
   return 0 ;
}


/* Calculate the average. */
double average(double value1, double value2) {
   double avgValue ;

   avgValue = (value1 + value2) / 2.0 ;

   return avgValue ;
}