Program for function without return type and without arguments

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/*Program for  function without return type and without arguments*/
#include<iostream.h>
#include<conio.h>
void main()
{
clrscr();
void sum(); //Function Declaration
cout<<"Sum of two number:";
sum(); //Function call
getch();
}
void  sum() //Function Definition
{
int a,b,c;
a=5;
b=6;
c=a+b;
cout<<c;
}