Module Scalar_Product.h:

/*prototype of the function*/
float Scalar_Product(int, float[], float[]);


Module main.c:

#include <stdio.h>
#include <stdlib.h>

#include "Scalar_Product.h"

#define MAX_INDEX 5

int main()
{
int n,i;
float x[MAX_INDEX], y[MAX_INDEX];
printf("\n Vector dimension n=");
scanf("%d",&n);

if(n < 1 || n > MAX_INDEX)
 {
  printf("\n Error in input data!");
  exit(1);
 }

printf("Input %d coordinate x: ", n);
for (i=0; i<n; i++) scanf("%f", &x[i]);
printf("Input %d coordinate y: ", n);
for (i=0; i<n; i++) scanf("%f", &y[i]);
printf("\n Result: %7.3f \n", Scalar_Product(n,x,y));

exit(0);
}


Module Scalar_Product.c:

#include <stdio.h>

/* --- The function ---------*/
float Scalar_Product(int n, float a[], float b[])
/* n - dimension of the vectors */
/* a[], b[] - the vector coordinates */

{ int i;
  double z; 
  for (i=0,z=0.0; i < n; i++)
    z += a[i]*b[i];
  return z;
}