features of object-oriented programming

Object-oriented programming (OOP) is a programming paradigm that uses "objects" to design applications and computer programs. It uses several techniques from previously established paradigms, including inheritance, modularity, polymorphism, and encapsulation.
Object-oriented programming may be seen as a collection of cooperating objects, as opposed to a traditional view in which a program may be seen as a list of instructions to the computer. In OOP, each object is capable of receiving messages, processing data, and sending messages to other objects. Each object can be viewed as an independent little machine with a distinct role or responsibility.

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In object-oriented programming, inheritance is a way to form new classes (instances of which are called objects) using classes that have already been defined. The new classes, known as derived classes, take over (or inherit) attributes and behavior of the pre-existing classes, which are referred to as base classes (or ancestor classes). It is intended to help reuse existing code with little or no modification.

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In object-oriented programming, a class is a programming language construct that is used to group related instance variables and methods. A method, called a function in some languages, is a set of instructions that are specific to a class. Depending on the language, classes may support multiple inheritance or may require the use of interfaces to extend other classes. A class may indicate either specifically or abstractly what methods exist when the program is executed. The latter is known as an 'abstract class'. A class must be defined with a constructor if it is to be used as an object, that is, instantiated. However some classes, especially those containing factory methods, are defined as static classes with no constructor merely to organize data hierarchically (e.g. the Math class may contain the static constant PI and the static method abs).