It’s just a syntax, nothing more than that for saying that “the function is pure virtual”.
A pure virtual function is a virtual function in C++ for which we need not to write any function definition and only we have to declare it. It is declared by assigning 0 in declaration.
Here is an example of pure virtual function in C++ program
#include<iostream> using namespace std; class B { public: virtual void s() = 0; // Pure Virtual Function }; class D:public B { public: void s() { cout << " Virtual Function in Derived class\n"; } }; int main() { B *b; D dobj; b = &dobj; b->s(); }
Virtual Function in Derived class