(48)typeid
typeid is used to get the Type for a type at compile time.

(49)typename
Tells the compiler that an unknown identifier is a type.Use this keyword only in template definitions.

(50)union
声明联合数据类型.A union is a user-defined data or class type that, at any given time, contains only one object from its list of members (although that object can be an array or a class type).

(51)using
The using declaration introduces a name into the declarative region in which the using declaration appears.

(52)virtual
声明虚基类或虚函数.The virtual keyword declares a virtual function or a virtual base class.

(53)void
声明函数无返回值或无参数，声明无类型指针.
When used as a function return type, the void keyword specifies that the function does not return a value. When used for a function’s parameter list, void specifies that the function takes no parameters. When used in the declaration of a pointer, void specifies that the pointer is “universal.”

(54)volatile
说明变量在程序执行中可被隐含地改变,表明某个变量的值可能在外部被改变，优化器在用到这个变量时必须每次都小心地重新读取这个变量的值，而不是使用保存在寄存器里的备份。The volatile keyword is a type qualifier used to declare that an object can be modified in the program by something such as the operating system, the hardware, or a concurrently executing thread.

(55)wchar_t
宽字.

(56)while
循环语句的循环条件