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In object-oriented programming, inheritance is the mechanism of basing an object or class upon another object or class , retaining similar implementation. Also defined as deriving new classes from existing ones such as super class or base class and then forming them into a hierarchy of classes. In most class-based object-oriented languages, an object created through inheritance, a "child object", acquires all the properties and behaviors of the "parent object" , with the exception of: constructors, destructor, overloaded operators and friend functions of the base class. Inheritance allows programmers to create classes that are built upon existing classes, to specify a new implementation while maintaining the same behaviors , to reuse code and to independently extend original software via public classes and interfaces. The relationships of objects or classes through inheritance give rise to a directed acyclic graph.
Inheritance was invented in 1969 for Simula and is now used throughout many object-oriented programming languages such as Java, C++, PHP and Python.
An inherited class is called a subclass of its parent class or super class. The term "inheritance" is loosely used for both class-based and prototype-based programming, but in narrow use the term is reserved for class-based programming , with the corresponding technique in prototype-based programming being instead called delegation.
Inheritance should not be confused with subtyping. In some languages inheritance and subtyping agree, whereas in others they differ; in general, subtyping establishes an is-a relationship, whereas inheritance only reuses implementation and establishes a syntactic relationship, not necessarily a semantic relationship. To distinguish these concepts, subtyping is sometimes referred to as interface inheritance , whereas inheritance as defined here is known as implementation inheritance or code inheritance. Still, inheritance is a commonly used mechanism for establishing subtype relationships.