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override keyword in c++ | C++ 11

Override Keyword (for virtual function) :
// C++ 03
class CAT {
   virtual void A(int);
   virtual void B() const;
}

 class YellowCAT : public CAT {
   virtual void A(float);  // Created a new function
   virtual void B(); // Created a new function 
}

 In C++, the intention of user was to override both function A and B, but since the function signature mismatch in function A and const keyword mismatch in function B. hence function A and B will not get override at run time.
// C++ 11
class CAT {
   virtual void A(int);
   virtual void B() const;
   void C();
}

 class YellowCAT : public CAT {
   virtual void A(float) override;  // Error: no function to override
   virtual void B() override;       // Error: no function to override
   void C() override;               // Error: not a virtual function
}

 With override keyword, the above functions results an error message, as there is no such functions defined in base class.

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