Function Overloading vs Function Overriding in C++

Function Overloading (achieved at compile time)

It provides multiple definitions of the function by changing signature i.e changing number of parameters, change datatype of parameters, return type doesn’t play anyrole.

  • It can be done in base as well as derived class.
  • Example:
    void area(int a);
    void area(int a, int b); 
    
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// 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;
}

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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";};
    }
    
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// 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's display method
    void Display()
    {
        cout << "\nThis is Display() method"
               " of DerivedClass";
    }
};
  
// Driver code
int main()
{
    DerivedClass dr;
    BaseClass &bs = dr;
    bs.Display();
    dr.Show();
}

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Output:

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

Function Overloading VS Function Overriding

  1. Inheritance: Overriding of functions occurs when one class is inherited from another class. Overloading can occur without inheritance.
  2. Function Signature: Overloaded functions must differ in function signature ie either number of parameters or type of parameters should differ. In overriding, function signatures must be same.
  3. Scope of functions: Overridden functions are in different scopes; whereas overloaded functions are in same scope.
  4. Behavior of functions: Overriding is needed when derived class function has to do some added or different job than the base class function. Overloading is used to have same name functions which behave differently depending upon parameters passed to them.

This article is contributed by Mazhar Mik and Yash Singla. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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