Function Overloading vs Overriding in C++

Function Overloading vs Overriding in C++

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Prerequisites

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1. What are Overloading and Overriding

C++ supports two important polymorphism concepts:

• Overloading → Same function name, different parameters
• Overriding → Same function signature, different implementation (inheritance)

Feature	Overloading	Overriding
Scope	Same class	Inheritance
Function name	Same	Same
Parameters	Different	Same
Binding	Compile-time	Runtime
Keyword	None	virtual, override

2. Overloading

Multiple functions with the same name but different parameter lists

✔ Example

int add(int a, int b) 
{
    return a + b;
}

double add(double a, double b) 
{
    return a + b;
}

Same name add, different parameter types

• Happens at compile-time (static polymorphism)
• Based on:
  • Number of parameters
  • Type of parameters
• Return type alone is NOT enough

❌ Invalid Overloading

int foo(int a);
double foo(int a);  // ❌ error

• Resolved at compile-time → fast

3. Overriding

Derived class provides a new implementation of a base class virtual function

✔ Example

class Base 
{
public:
    virtual void print()
    {
        std::cout << "Base\n";
    }
};

class Derived : public Base 
{
public:
    void print() override 
    {
        std::cout << "Derived\n";
    }
};

✔ Usage

Base* obj = new Derived();
obj->print();  // Output: Derived

Runtime polymorphism

• Requires virtual function
• Happens at runtime
• Uses vtable (virtual table)
• Uses vtable lookup → small runtime cost