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Abstraction is a fundamental concept in computer science and software engineering, especially within the object-oriented programming paradigm. [3] Examples of this include: the usage of abstract data types to separate usage from working representations of data within programs; [4]
In object oriented programming, objects provide a layer which can be used to separate internal from external code and implement abstraction and encapsulation. External code can only use an object by calling a specific instance method with a certain set of input parameters, reading an instance variable, or writing to an instance variable.
Abstraction Definition Usage Variable: A storage location paired with an associated symbolic name that contains some known or unknown quantity of information referred to as a value. Typically used in all programming paradigms. Function: An abstraction representing a set of instructions that can be applied to input data to produce output.
Separate an abstraction (Abstraction) from its implementation (Implementor) by putting them in separate class hierarchies. Implement the Abstraction in terms of (by delegating to) an Implementor object. This enables to configure an Abstraction with an Implementor object at run-time. See also the Unified Modeling Language class and sequence ...
The abstraction principle is mentioned in several books. Some of these, together with the formulation if it is succinct, are listed below. Alfred John Cole, Ronald Morrison (1982) An introduction to programming with S-algol: "[Abstraction] when applied to language design is to define all the semantically meaningful syntactic categories in the language and allow an abstraction over them".
Liskov substitution principle imposes some standard requirements on signatures that have been adopted in newer object-oriented programming languages (usually at the level of classes rather than types; see nominal vs. structural subtyping for the distinction): Contravariance of method parameter types in the subtype.
In object-oriented programming, an interface or protocol type [a] is a data type that acts as an abstraction of a class. It describes a set of method signatures, the implementations of which may be provided by multiple classes that are otherwise not necessarily related to each other. [1]
All object-oriented programming (OOP) systems support encapsulation, [2] [3] but encapsulation is not unique to OOP. Implementations of abstract data types, modules, and libraries also offer encapsulation. The similarity has been explained by programming language theorists in terms of existential types. [4]