Templates in C++ is an interesting feature that is used for generic programming and templates in C++ is defined as a blueprint or formula for creating a generic class or a function. Simply put, you can create a single function or single class to work with different data types using templates. C++ template is also known as generic functions or classes which is a very powerful feature in C++. 

A keyword “template” in C++ is used for the template’s syntax and angled bracket in a parameter (t), which defines the data type variable.


Class Template:

A class template starts with the keyword template followed by template parameter(s) inside <> which is followed by the class declaration

#include<iostream>
using namespace std;
template< class T >
class num
{
    public:
    T number;
    num ( T n )
    {
        number = n;
    }
    T returnnum()
    {
        return number;
    }
};
int main()
{
    num < int > obj1( 5 );
    cout << " Int = "<< obj1.returnnum();
    
    num < float > obj2( 2.3 );
    cout << " Float = " << obj2.returnnum();
}

Output:
Int = 5
Float = 2.3


Making a Simple Calculator using a class template:

#include<iostream>
using namespace std;
template <class T>
class calc
{
    T n,m;
    public:
    calc(T n1,T n2)
    {
        n=n1;
        m=n2;
    }
    T sub()
    {
        return n-m;
    }
    T mul()
    {
        return n*m;
    }
    T divv()
    {
        return n/m;
    }
    T add()
    {
        return n+m;
    }
    void disp()
    {
        cout<<"add = "<<add()<<endl;
        cout<<"sub = "<<sub()<<endl;
        cout<<"mul = "<<mul()<<endl;
        cout<<"div = "<<divv()<<endl;
    }
};
int main()
{
    calc < int > obj(10,5);
    obj.disp();
}

Output:
add = 15
sub = 5
mul = 50
div = 2


Function Template:

A function template starts with the keyword template followed by template parameter(s) inside <> which is followed by the function definition.

#include<iostream>
using namespace std;
template < typename T >
T add ( T n1 , T n2 )
{
    return n1 + n2;
}
int main()
{
    int r1;
    float r2;
    r1 = add < int > ( 1 , 2 );
    cout << " int addition " << r1 << endl;
    r2 = add < float > ( 1.1 , 2.2 );
    cout << " float addition " << r2 << endl;
    
}

Output:
int addition 3
float addition 3.3


Swapping numbers using function template

#include < iostream >
using namespace std;
template < typename T >
void swap ( T n1 , T n2 )
{
    cout << " Nos before swapping are: " << endl;
    cout << " n1 = " <<  n1 << " , n2 =  " << n2 << endl;
    T temp;
    temp = n1;
    n1 = n2;
    n2 = temp;
    cout << " Nos after swapping are: " << endl;
    cout << " n1 = " << n1 << " , n2 = " << n2 << endl;
}
int main()
{
    swap < int > ( 2 , 3 );
    swap < float > ( 2.2 , 3.3 );
      
}

Output:
Nos before swapping are: n1 = 2 , n2 = 3
Nos before swapping are: n1 = 3 , n2 = 2
Nos before swapping are: n1 = 2.2 , n2 = 3.3
Nos before swapping are: n1 = 3.3 , n2 = 2.2