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1. What and why is explicit constructor and explicit copy constructor? 2. What the difference between Struct and Class? 3. What is vitrual function and why we need vtable? 1. Explicit constructor and copy constructor is used to preventing implicit type cast. An explicit constructor can not take part in implicit conversions. It can only be? used to explicit construct an object Consider the Class below: class A { public: A(); A(int i); A(A a); int i; virtual ~A(); }; The following program will success to compile : A a = 10; or A a; a = 10; because A has a constructor that accept a Int as a arguments Those codes above are equal to A tmp(10);??? //constructor a(tmp);????? //copy constructor or A tmp(10) ;? //constructor a = tmp;???? // operator = Note: explicit on a constructor with mutiple arguments has no effect,? unless all? but one of the arguments has a default value ! 2: differences between struct and class? 3 difference between struct and class 1)members in struct are by default public while members in class are by default? private. 2)inhert? from? a struct is by default public , inhert from a class is by default private. For example struct A { }; struct B : (public)A { } ; class A { }; class B: (private)A { }; 3)class can be used as typename in template while struct can not template(class T)????? //right template(struct T)???? //wrong 3: What is virtual function and why we need vtable? 1) a virtual function is a function member of a class decleared with a virtual? keyword 2) it usually has a different functionality in the derived class 3) A function is resolved at run-time The main difference between a non_virtual function and a virtual? function is, the? non_virtual function is resolved at compile time. This? mechanism is called? static_binding.? As the virtual function is? resolved at run time, This mechanism is? know as dynamic_binding v_table is kind of lookup table.It contains pointers to the virtual? functions provided? by a class, and each object of the c