What is the difference between virtual function instances in C ++?

Question

What is the difference between the next two ads?

virtual void calculateBase() = 0;  
virtual void calculateBase();

I read the first (= 0) - "pure abstract function", but what does the second do?

Answer 1

The first is called a pure virtual function. Normally, pure virtual functions have no implementation, and you cannot instantiate a class containing a pure virtual function.

The second is a virtual function (that is, a "normal" virtual function). A class provides an implementation for this function, but its derived class can override this implementation by providing its own implementation for this method.

Answer 2

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Answer 3

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Answer 4

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Java, ?

Answer 5

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virtual void x() = 0;

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virtual void x();

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Answer 6

virtual void calculateBase() = 0;

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void calculateBase();

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Answer 7

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Answer 8

Java

virtual void calculateBase() = 0;  

abstract void calculateBase();

virtual void calculateBase();

void calculateBase();

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void calculateBase();

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final void calculateBase();

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