Function overloading and using templates are extremely useful when trying to not write duplicate methods with the same parameters, but only different types.

//main.cpp
#include <iostream>

using namespace std;

void get2Values  (int &data1, int &data2);
void get2Values  (double &data1, double &data2);

void print2Values  (const int &data1,const int &data2);
void print2Values (const double &data1,const double &data2);

template <class dataType>
void  swapC (dataType &a,  dataType &b);

int main ()
{
   int first, second;
   double dFirst, dSecond;

    get2Values(first, second);
    get2Values(dFirst, dSecond);

    print2Values(first, second);
    print2Values(dFirst, dSecond);

    cout << endl << "--Swap--" ;

    swapC<int>(first, second);
    swapC<double>(dFirst, dSecond);

    print2Values(first, second);
    print2Values(dFirst, dSecond);

	cout << endl;
	cin.get();
	return 0;
}

void  get2Values (double &data1, double &data2)
{
	cout << "Enter Double 1 ---> ";
	cin >> data1;
	cout << "Enter Double 2 ---> ";
	cin >> data2;
}

void  get2Values (int &data1, int &data2)
{
	cout << "Enter int 1 ---> ";
	cin >> data1;
	cout << "Enter int 2 ---> ";
	cin >> data2;
}

void  print2Values (const double &data1,const double &data2)
{
	cout << endl << "Double 1 ---> " << data1;
	cout << endl << "Double 2 ---> " << data2;
}
void  print2Values (const int &data1,const int &data2)
{
	cout << endl << "Int 1 ---> " << data1;
	cout << endl << "Int 2 ---> " << data2;
}

template <class dataType>
void  swapC (dataType &a,  dataType &b)
{
	dataType temp = a;  a = b;  b = temp;
}

The output should be:

Enter int 1 ---> 1
Enter int 2 ---> 2
Enter Double 1 ---> 3.21
Enter Double 2 ---> 8.125647

Int 1 ---> 1
Int 2 ---> 2
Double 1 ---> 3.21
Double 2 ---> 8.12565
--Swap--
Int 1 ---> 2
Int 2 ---> 1
Double 1 ---> 8.12565
Double 2 ---> 3.21

The template function allows you to pass in any value, saving you from creating the two methods above unique to double and int.