C++ classes offer extensions to the predefined type system. Each class type represents a unique set of objects and the operations (methods) and conversions available to create, manipulate, and destroy such objects. Derived classes can be declared that inherit the members of one or more base (or parent) classes. 

In C++, structures and unions are considered classes with certain access defaults. 

A simplified, “first-look” syntax for class declarations is 

class-key <type-info> class-name  

<: base-list> { <member-list> }; 

class-key is one of class, struct, or union. 

The optional type-info indicates a request for runtime type information about the class. You can compile with the –RT compiler option, or you can use the __rtti keyword. 

The optional base-list lists the base class or classes from which the class class-name will derive (or inherit) objects and methods. If any base classes are specified, the class class-name is called a derived class. The base-list has default and optional overriding access specifiers that can modify the access rights of the derived class to members of the base classes. 

The optional member-list declares the class members (data and functions) of class-name with default and optional overriding access specifiers that can affect which functions can access which members.