Can you explain what the term 'virtual' means in the context of programming and how it is used?

In programming, especially in C++, the keyword virtual is used to declare virtual functions — methods that can be overridden in derived classes and provide dynamic (polymorphic) calls.

This means that when calling a method through a pointer or reference to the base class, the version of the method corresponding to the actual type of the object will be called, not the type of the pointer.

Example:

#include <iostream>

class Base {
public:
    virtual void show() { // virtual function
        std::cout << "Base show" << std::endl;
    }
};

class Derived : public Base {
public:
    void show() override { // override
        std::cout << "Derived show" << std::endl;
    }
};

int main() {
    Base* ptr = new Derived();
    ptr->show(); // calls Derived::show thanks to virtual
    delete ptr;
    return 0;
}

If you remove virtual, then calling ptr->show() will invoke the base class method, even if the object is actually of type Derived.

Thus, virtual enables the implementation of polymorphism — an important principle of object-oriented programming.