A class is a mechanism for creating user-defined data types. It is similar to the C language structure data type. In C, a structure is composed of a set of data members. In C++, a class type is like a C structure, except that a class is composed of a set of data members and a set of operations that can be performed on the class.
In C++, a class type can be declared with the keywords union, struct, or class. A union object can hold any one of a set of named members. Structure and class objects hold a complete set of members. Each class type represents a unique set of class members including data members, member functions, and other type names. The default access for members depends on the class key:
Once you create a class type, you can declare one or more objects of that class type. For example:
class X
{
/* define class members here */
};
int main()
{
X xobject1; // create an object of class type X
X xobject2; // create another object of class type X
}You may have polymorphic classes in C++. Polymorphism is the ability to use a function name that appears in different classes (related by inheritance), without knowing exactly the class the function belongs to at compile time.
C++ allows you to redefine standard operators and functions through the concept of overloading. Operator overloading facilitates data abstraction by allowing you to use classes as easily as built-in types.
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