Function Overloading vs Function Overriding in C++

Function Overloading (achieved at compile time)

Function Overloading provides multiple definitions of the function by changing signature i.e. changing number of parameters, change datatype of parameters, return type doesn’t play any role. 

• It can be done in base as well as derived class
  .Example:

void area(int a);
void area(int a, int b); 

CPP

// CPP program to illustrate
// Function Overloading
#include <iostream>
using namespace std;

// overloaded functions
void test(int);
void test(float);
void test(int, float);

int main()
{
    int a = 5;
    float b = 5.5;

    // Overloaded functions
    // with different type and
    // number of parameters
    test(a);
    test(b);
    test(a, b);

    return 0;
}

// Method 1
void test(int var)
{
    cout << "Integer number: " << var << endl;
}

// Method 2
void test(float var)
{
    cout << "Float number: "<< var << endl;
}

// Method 3
void test(int var1, float var2)
{
    cout << "Integer number: " << var1;
    cout << " and float number:" << var2;
}

Output

Integer number: 5
Float number: 5.5
Integer number: 5 and float number:5.5

Function Overriding (achieved at run time)

It is the redefinition of base class function in its derived class with same signature i.e. return type and parameters. 

• It can only be done in derived class.
• Example:

Class a
{
public: 
      virtual void display(){ cout << "hello"; }
};

Class b:public a
{
public: 
       void display(){ cout << "bye";}
};
 

CPP

// CPP program to illustrate
// Function Overriding
#include<iostream>
using namespace std;

class BaseClass
{
public:
    virtual void Display()
    {
        cout << "\nThis is Display() method"
                " of BaseClass";
    }
    void Show()
    {
        cout << "\nThis is Show() method "
               "of BaseClass";
    }
};

class DerivedClass : public BaseClass
{
public:
    // Overriding method - new working of
    // base class display method
    void Display()
    {
        cout << "\nThis is Display() method"
               " of DerivedClass";
    }
};

// Driver code
int main()
{
    DerivedClass dr;
    BaseClass &bs = dr;
    bs.Display();
    dr.Show();
}

Output

This is Display() method of DerivedClass
This is Show() method of BaseClass

Function Overloading	Function Overriding
Function Overloading provides multiple definitions of the function by changing signature.	Function Overriding is the redefinition of base class function in its derived class with same signature.
An example of compile time polymorphism.	An example of run time polymorphism.
Function signatures should be different.	Function signatures should be the same.
Overloaded functions are in same scope.	Overridden functions are in different scopes.
Overloading is used when the same function has to behave differently depending upon parameters passed to them.	Overriding is needed when derived class function has to do some different job than the base class function.
A function has the ability to load multiple times.	A function can be overridden only a single time.
In function overloading, we don’t need inheritance.	In function overriding, we need an inheritance concept.

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