C Progam to add two Numbers using Functions

This  is a simple program to add two Numbers 

#include<stdio.h>
#include<stdio.h>
#include<conio.h>
 void main()
 {
 int a,b,c;
 printf("\nEnter the two numbers : ");
 scanf("%d %d",&a,&b);

 /* Call Function Sum With Two Parameters */
 c = sum(a,b);

 printf("\nAddition of two number is : ");
 getch();
 }

 int sum ( int num1,int num2)
 {
 int num3;
 num3 = num1 + num2 ;
 return(num3);
 }