Deep understanding of common keyword meanings in C + + _c language

1. Inline: defines an inline function, which is based on a definition, and if inline is given only when the function is declared, the function is not considered an inline function, so it must be added to the function definition where the inline, At the same time, inline simply suggests to the compiler that the function be handled inline, not coerced.
2. Const: defines a constant member, including const data members and const member functions, the const data member must, and can only be initialized through the constructor's initialization list, the const member function can only access members of the class, cannot be modified, and if necessary, The following mutable keyword is introduced.
3.mutable: The introduction of this keyword is to resolve the const member function to modify the member variable, in general, the Const member function can only access the member variable and cannot be modified, but if the member variable is mutable modified, You can modify the variable in the const member function. Mutable and const cannot be used to modify member variables at the same time.
4. Static: declaring static members, including static data members and static member functions, they are shared by all objects of the class, static data members must be initialized before they are used, and static member functions can access only static data members, not non-static data members. Because the function does not contain the this pointer.
5. Virtual: declares a virtual function to implement polymorphism, which is based on a declaration.
6. Friend: declare the friend function and the friend class, which is also based on the declaration.
7. Volatile: A variable modified by this keyword means that its value may be modified outside the scope of the compiler's knowledge, so the compiler does not optimize the operation of the variable. You can also modify a variable with Const.