C program to find average of three numbers :

#include< stdio.h >
#include< conio.h >
void main()
{
           int num1,num2,num3;
           void avg (int a, int b, int c);
           clrscr();
           printf("Enter three numbers:");
           scanf("\n%d \n%d\n %d",&num1,&num2,&num3);
           avg(num1,num2,num3);
           getch();
}
void avg (int a, int b, int c)
{
          float avgg;
         avg=(a+b+c)/3.0;
         printf("Average of given numbers is=%f",avgg);
}

OUTPUT :

Enter three numbers:
5
8
6
Average of given numbers is=19