Object-oriented programming
Encyclopedia
Object-oriented programming (OOP) is a programming paradigm
using "objects
" – data structure
s consisting of data fields
and methods
together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction, encapsulation
, messaging
, modularity, polymorphism
, and inheritance
. Many modern programming language
s now support OOP, at least as an option.
s each of which might perform a particular task. With designs of this sort, it is common for some of the program's data to be 'global', i.e. accessible from any part of the program. As programs grow in size, allowing any function to modify any piece of data means that bugs can have wide-reaching effects.
In contrast, the object-oriented approach encourages the programmer to place data where it is not directly accessible by the rest of the program. Instead, the data is accessed by calling specially written functions, commonly called methods
, which are either bundled in with the data or inherited from "class objects." These act as the intermediaries for retrieving or modifying the data they control. The programming construct that combines data with a set of methods for accessing and managing those data is called an object. The practice of using subroutines to examine or modify certain kinds of data, however, was also quite commonly used in non-OOP modular programming
, well before the widespread use of object-oriented programming.
An object-oriented program will usually contain different types of objects, each type corresponding to a particular kind of complex data to be managed or perhaps to a real-world object or concept such as a bank account, a hockey player, or a bulldozer. A program might well contain multiple copies of each type of object, one for each of the real-world objects the program is dealing with. For instance, there could be one bank account object for each real-world account at a particular bank. Each copy of the bank account object would be alike in the methods it offers for manipulating or reading its data, but the data inside each object would differ reflecting the different history of each account.
Objects can be thought of as wrapping their data within a set of functions designed to ensure that the data are used appropriately, and to assist in that use. The object's methods will typically include checks and safeguards that are specific to the types of data the object contains. An object can also offer simple-to-use, standardized methods for performing particular operations on its data, while concealing the specifics of how those tasks are accomplished. In this way alterations can be made to the internal structure or methods of an object without requiring that the rest of the program be modified. This approach can also be used to offer standardized methods across different types of objects. As an example, several different types of objects might offer print methods. Each type of object might implement that print method in a different way, reflecting the different kinds of data each contains, but all the different print methods might be called in the same standardized manner from elsewhere in the program. These features become especially useful when more than one programmer is contributing code to a project or when the goal is to reuse code between projects.
Object-oriented programming has roots that can be traced to the 1960s. As hardware and software became increasingly complex, manageability often became a concern. Researchers studied ways to maintain software quality and developed object-oriented programming in part to address common problems by strongly emphasizing discrete, reusable units of programming logic. The technology focuses on data rather than processes, with programs composed of self-sufficient modules ("classes"), each instance of which ("objects") contains all the information needed to manipulate its own data structure ("members"). This is in contrast to the existing modular programming
that had been dominant for many years that focused on the function of a module, rather than specifically the data, but equally provided for code reuse
, and self-sufficient reusable units of programming logic, enabling collaboration
through the use of linked modules (subroutine
s).
This more conventional approach, which still persists, tends to consider data and behavior separately.
An object-oriented program may thus be viewed as a collection of interacting objects, as opposed to the conventional model, in which a program is seen as a list of tasks (subroutine
s) to perform. 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 "machine" with a distinct role or responsibility. The actions (or "methods
") on these objects are closely associated with the object. For example, OOP data structures tend to "carry their own operators around with them" (or at least "inherit
" them from a similar object or class) - except when they have to be serialized.
group, as early as 1960, "object" could refer to identified items (LISP
atoms) with properties (attributes);
Alan Kay was later to cite a detailed understanding of LISP internals as a strong influence on his thinking in 1966.
Another early MIT example was Sketchpad
created by Ivan Sutherland
in 1960-61; in the glossary of the 1963 technical report based on his dissertation about Sketchpad, Sutherland defined notions of "object" and "instance" (with the class concept covered by "master" or "definition"), albeit specialized to graphical interaction.
Also, an MIT ALGOL
version, AED-0, linked data structures ("plexes", in that dialect) directly with procedures, prefiguring what were later termed "messages", "methods" and "member functions".
Objects as a formal concept in programming were introduced in the 1960s in Simula
67, a major revision of Simula I, a programming language designed for discrete event simulation
, created by Ole-Johan Dahl
and Kristen Nygaard
of the Norwegian Computing Center
in Oslo
.
Simula 67 was influenced by SIMSCRIPT
and Hoare's proposed "record classes".
Simula introduced the notion of classes and instances or objects (as well as subclasses, virtual methods, coroutines, and discrete event simulation) as part of an explicit programming paradigm. The language also used automatic garbage collection
that had been invented earlier for the functional programming
language Lisp. Simula was used for physical modeling, such as models to study and improve the movement of ships and their content through cargo ports. The ideas of Simula 67 influenced many later languages, including Smalltalk, derivatives of LISP (CLOS
), Object Pascal
, and C++
.
The Smalltalk
language, which was developed at Xerox PARC
(by Alan Kay
and others) in the 1970s, introduced the term object-oriented programming to represent the pervasive use of objects and messages as the basis for computation. Smalltalk creators were influenced by the ideas introduced in Simula 67, but Smalltalk was designed to be a fully dynamic system in which classes could be created and modified dynamically rather than statically as in Simula 67. Smalltalk and with it OOP were introduced to a wider audience by the August 1981 issue of Byte Magazine
.
In the 1970s, Kay's Smalltalk work had influenced the Lisp community to incorporate object-based techniques that were introduced to developers via the Lisp machine
. Experimentation with various extensions to Lisp (like LOOPS and Flavors introducing multiple inheritance
and mixins), eventually led to the Common Lisp Object System (CLOS, a part of the first standardized object-oriented programming language, ANSI
Common Lisp
), which integrates functional programming and object-oriented programming and allows extension via a Meta-object protocol. In the 1980s, there were a few attempts to design processor architectures that included hardware support for objects in memory but these were not successful. Examples include the Intel iAPX 432
and the Linn Smart
Rekursiv
.
Object-oriented programming developed as the dominant programming methodology in the early and mid 1990s when programming languages supporting the techniques became widely available. These included Visual FoxPro 3.0, C++
, and Delphi. Its dominance was further enhanced by the rising popularity of graphical user interface
s, which rely heavily upon object-oriented programming techniques. An example of a closely related dynamic GUI library and OOP language can be found in the Cocoa frameworks on Mac OS X
, written in Objective-C
, an object-oriented, dynamic messaging extension to C based on Smalltalk. OOP toolkits also enhanced the popularity of event-driven programming
(although this concept is not limited to OOP). Some feel that association with GUIs (real or perceived) was what propelled OOP into the programming mainstream.
At ETH Zürich
, Niklaus Wirth
and his colleagues had also been investigating such topics as data abstraction and modular programming
(although this had been in common use in the 1960s or earlier). Modula-2
(1978) included both, and their succeeding design, Oberon
, included a distinctive approach to object orientation, classes, and such. The approach is unlike Smalltalk, and very unlike C++.
Object-oriented features have been added to many existing languages during that time, including Ada
, BASIC
, Fortran
, Pascal
, and others. Adding these features to languages that were not initially designed for them often led to problems with compatibility and maintainability of code.
More recently, a number of languages have emerged that are primarily object-oriented yet compatible with procedural methodology, such as Python
and Ruby. Probably the most commercially important recent object-oriented languages are Visual Basic.NET (VB.NET) and C#, both designed for Microsoft's .NET
platform, and Java
, developed by Sun Microsystems
. Both frameworks show the benefit of using OOP by creating an abstraction from implementation in their own way. VB.NET and C# support cross-language inheritance, allowing classes defined in one language to subclass classes defined in the other language. Developers usually compile Java to bytecode
, allowing Java to run on any operating system for which a Java virtual machine
is available. VB.NET and C# make use of the Strategy pattern
to accomplish cross-language inheritance, whereas Java makes use of the Adapter pattern
.
Just as procedural programming
led to refinements of techniques such as structured programming
, modern object-oriented software design methods include refinements such as the use of design patterns
, design by contract
, and modeling language
s (such as UML
).
Not all of these concepts are to be found in all object-oriented programming languages. For example, object-oriented programming that uses classes is sometimes called class-based programming
, while prototype-based programming
does not typically use classes. As a result, a significantly different yet analogous terminology is used to define the concepts of object and instance.
Benjamin C. Pierce and some other researchers view as futile any attempt to distill OOP to a minimal set of features. He nonetheless identifies fundamental features that support the OOP programming style in most object-oriented languages:
Similarly, in his 2003 book, Concepts in programming languages, John C. Mitchell identifies four main features: dynamic dispatch, abstraction
, subtype polymorphism, and inheritance. Michael Lee Scott in Programming Language Pragmatics considers only encapsulation, inheritance and dynamic dispatch.
Additional concepts used in object-oriented programming include:
and Adapter pattern
) - for example, using a method interface which an encapsulated object must satisfy, as opposed to using the object's class.
Attempts to find a consensus definition or theory behind objects have not proven very successful (however, see Abadi & Cardelli, A Theory of Objects for formal definitions of many OOP concepts and constructs), and often diverge widely. For example, some definitions focus on mental activities, and some on program structuring. One of the simpler definitions is that OOP is the act of using "map" data structures or arrays that can contain functions and pointers to other maps, all with some syntactic and scoping sugar on top. Inheritance can be performed by cloning the maps (sometimes called "prototyping").
OBJECT:=>>
Objects are the run time entities in an object-oriented system. They may represent a person, a place, a bank account, a table of data or any item that the program has to handle.
(1967) is generally accepted as the first language to have the primary features of an object-oriented language. It was created for making simulation program
s, in which what came to be called objects were the most important information representation. Smalltalk
(1972 to 1980) is arguably the canonical example, and the one with which much of the theory of object-oriented programming was developed. Concerning the degree of object orientation, following distinction can be made:
s. Python
, Ruby
and Groovy are dynamic languages built on OOP principles, while Perl
and PHP
have been adding object oriented features since Perl 5 and PHP 4, and ColdFusion
since version 5.
The Document Object Model
of HTML
, XHTML
, and XML
documents on the Internet have bindings to the popular JavaScript
/ECMAScript
language. JavaScript is perhaps the best known prototype-based programming
language, which employs cloning from prototypes rather than inheriting from a class. Another scripting language that takes this approach is Lua. Earlier versions of ActionScript
(a partial superset of the ECMA-262 R3, otherwise known as ECMAScript) also used a prototype-based object model. Later versions of ActionScript incorporate a combination of classification and prototype-based object models based largely on the currently incomplete ECMA-262 R4 specification, which has its roots in an early JavaScript 2 Proposal. Microsoft's JScript.NET also includes a mash-up of object models based on the same proposal, and is also a superset of the ECMA-262 R3 specification.
" can be used to refer to any general, repeatable solution to a commonly occurring problem in software design. Some of these commonly occurring problems have implications and solutions particular to object-oriented development.
as enforced by the type checker in OOP languages (with mutable objects) cannot guarantee behavioral subtyping in any context. Behavioral subtyping is undecidable in general, so it cannot be implemented by a program (compiler). Class or object hierarchies need to be carefully designed considering possible incorrect uses that cannot be detected syntactically. This issue is known as the Liskov substitution principle
.
, Richard Helm, Ralph Johnson, and John Vlissides
, sometimes casually called the "Gang of Four". Along with exploring the capabilities and pitfalls of object-oriented programming, it describes 23 common programming problems and patterns for solving them.
As of April 2007, the book was in its 36th printing.
The book describes the following patterns:
s don't store objects directly (though some RDBMSs have object-oriented features to approximate this), there is a general need to bridge the two worlds. The problem of bridging object-oriented programming accesses and data patterns with relational databases is known as Object-Relational impedance mismatch
. There are a number of approaches to cope with this problem, but no general solution without downsides. One of the most common approaches is object-relational mapping
, as found in libraries like Java Data Objects
and Ruby on Rails
' ActiveRecord.
There are also object database
s that can be used to replace RDBMSs, but these have not been as technically and commercially successful as RDBMSs.
argues in Object-Oriented Software Construction
that a program is not a model of the world but a model of some part of the world; "Reality is a cousin twice removed". At the same time, some principal limitations of OOP had been noted.
For example, the Circle-ellipse problem
is difficult to handle using OOP's concept of inheritance
.
However, Niklaus Wirth
(who popularized the adage now known as Wirth's law
: "Software is getting slower more rapidly than hardware becomes faster") said of OOP in his paper, "Good Ideas through the Looking Glass", "This paradigm closely reflects the structure of systems 'in the real world', and it is therefore well suited to model complex systems with complex behaviours" (contrast KISS principle
).
Steve Yegge
and others noted that natural languages lack the OOP approach of strictly prioritizing things (objects/noun
s) before actions (methods/verb
s). This problem may cause OOP to suffer more convoluted solutions than procedural programming.
and maintainability
of source code. Transparent representation of the control flow
had no priority and was meant to be handled by a compiler. With the increasing relevance of parallel hardware and multithreaded coding
, developer transparent control flow becomes more important, something hard to achieve with OOP.
defines classes in terms of a contract, that is, a class should be defined around a responsibility and the information that it shares. This is contrasted by Wirfs-Brock and Wilkerson with data-driven design
, where classes are defined around the data-structures that must be held. The authors hold that responsibility-driven design is preferable.
Programming paradigm
A programming paradigm is a fundamental style of computer programming. Paradigms differ in the concepts and abstractions used to represent the elements of a program and the steps that compose a computation A programming paradigm is a fundamental style of computer programming. (Compare with a...
using "objects
Object (computer science)
In computer science, an object is any entity that can be manipulated by the commands of a programming language, such as a value, variable, function, or data structure...
" – data structure
Data structure
In computer science, a data structure is a particular way of storing and organizing data in a computer so that it can be used efficiently.Different kinds of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks...
s consisting of data fields
Field (computer science)
In computer science, data that has several parts can be divided into fields. Relational databases arrange data as sets of database records, also called rows. Each record consists of several fields; the fields of all records form the columns....
and methods
Method (computer science)
In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...
together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction, encapsulation
Encapsulation (object-oriented programming)
In a programming language encapsulation is used to refer to one of two related but distinct notions, and sometimes to the combination thereof:* A language mechanism for restricting access to some of the object's components....
, messaging
Message passing
Message passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes...
, modularity, polymorphism
Polymorphism in object-oriented programming
Subtype polymorphism, almost universally called just polymorphism in the context of object-oriented programming, is the ability to create a variable, a function, or an object that has more than one form. The word derives from the Greek "πολυμορφισμός" meaning "having multiple forms"...
, and inheritance
Inheritance (computer science)
In object-oriented programming , inheritance is a way to reuse code of existing objects, establish a subtype from an existing object, or both, depending upon programming language support...
. Many modern programming language
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
s now support OOP, at least as an option.
Overview
Simple, non-OOP programs may be one "long" list of statements (or commands). More complex programs will often group smaller sections of these statements into functions or subroutineSubroutine
In computer science, a subroutine is a portion of code within a larger program that performs a specific task and is relatively independent of the remaining code....
s each of which might perform a particular task. With designs of this sort, it is common for some of the program's data to be 'global', i.e. accessible from any part of the program. As programs grow in size, allowing any function to modify any piece of data means that bugs can have wide-reaching effects.
In contrast, the object-oriented approach encourages the programmer to place data where it is not directly accessible by the rest of the program. Instead, the data is accessed by calling specially written functions, commonly called methods
Method (computer science)
In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...
, which are either bundled in with the data or inherited from "class objects." These act as the intermediaries for retrieving or modifying the data they control. The programming construct that combines data with a set of methods for accessing and managing those data is called an object. The practice of using subroutines to examine or modify certain kinds of data, however, was also quite commonly used in non-OOP modular programming
Modular programming
Modular programming is a software design technique that increases the extent to which software is composed of separate, interchangeable components called modules by breaking down program functions into modules, each of which accomplishes one function and contains everything necessary to accomplish...
, well before the widespread use of object-oriented programming.
An object-oriented program will usually contain different types of objects, each type corresponding to a particular kind of complex data to be managed or perhaps to a real-world object or concept such as a bank account, a hockey player, or a bulldozer. A program might well contain multiple copies of each type of object, one for each of the real-world objects the program is dealing with. For instance, there could be one bank account object for each real-world account at a particular bank. Each copy of the bank account object would be alike in the methods it offers for manipulating or reading its data, but the data inside each object would differ reflecting the different history of each account.
Objects can be thought of as wrapping their data within a set of functions designed to ensure that the data are used appropriately, and to assist in that use. The object's methods will typically include checks and safeguards that are specific to the types of data the object contains. An object can also offer simple-to-use, standardized methods for performing particular operations on its data, while concealing the specifics of how those tasks are accomplished. In this way alterations can be made to the internal structure or methods of an object without requiring that the rest of the program be modified. This approach can also be used to offer standardized methods across different types of objects. As an example, several different types of objects might offer print methods. Each type of object might implement that print method in a different way, reflecting the different kinds of data each contains, but all the different print methods might be called in the same standardized manner from elsewhere in the program. These features become especially useful when more than one programmer is contributing code to a project or when the goal is to reuse code between projects.
Object-oriented programming has roots that can be traced to the 1960s. As hardware and software became increasingly complex, manageability often became a concern. Researchers studied ways to maintain software quality and developed object-oriented programming in part to address common problems by strongly emphasizing discrete, reusable units of programming logic. The technology focuses on data rather than processes, with programs composed of self-sufficient modules ("classes"), each instance of which ("objects") contains all the information needed to manipulate its own data structure ("members"). This is in contrast to the existing modular programming
Modular programming
Modular programming is a software design technique that increases the extent to which software is composed of separate, interchangeable components called modules by breaking down program functions into modules, each of which accomplishes one function and contains everything necessary to accomplish...
that had been dominant for many years that focused on the function of a module, rather than specifically the data, but equally provided for code reuse
Code reuse
Code reuse, also called software reuse, is the use of existing software, or software knowledge, to build new software.-Overview:Ad hoc code reuse has been practiced from the earliest days of programming. Programmers have always reused sections of code, templates, functions, and procedures...
, and self-sufficient reusable units of programming logic, enabling collaboration
Collaboration
Collaboration is working together to achieve a goal. It is a recursive process where two or more people or organizations work together to realize shared goals, — for example, an intriguing endeavor that is creative in nature—by sharing...
through the use of linked modules (subroutine
Subroutine
In computer science, a subroutine is a portion of code within a larger program that performs a specific task and is relatively independent of the remaining code....
s).
This more conventional approach, which still persists, tends to consider data and behavior separately.
An object-oriented program may thus be viewed as a collection of interacting objects, as opposed to the conventional model, in which a program is seen as a list of tasks (subroutine
Subroutine
In computer science, a subroutine is a portion of code within a larger program that performs a specific task and is relatively independent of the remaining code....
s) to perform. 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 "machine" with a distinct role or responsibility. The actions (or "methods
Method (computer science)
In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...
") on these objects are closely associated with the object. For example, OOP data structures tend to "carry their own operators around with them" (or at least "inherit
Inheritance (object-oriented programming)
In object-oriented programming , inheritance is a way to reuse code of existing objects, establish a subtype from an existing object, or both, depending upon programming language support...
" them from a similar object or class) - except when they have to be serialized.
History
The terms "objects" and "oriented" in something like the modern sense of object-oriented programming seem to make their first appearance at MIT in the late 1950s and early 1960s. In the environment of the artificial intelligenceArtificial intelligence
Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...
group, as early as 1960, "object" could refer to identified items (LISP
Lisp
A lisp is a speech impediment, historically also known as sigmatism. Stereotypically, people with a lisp are unable to pronounce sibilants , and replace them with interdentals , though there are actually several kinds of lisp...
atoms) with properties (attributes);
Alan Kay was later to cite a detailed understanding of LISP internals as a strong influence on his thinking in 1966.
Another early MIT example was Sketchpad
Sketchpad
Sketchpad was a revolutionary computer program written by Ivan Sutherland in 1963 in the course of his PhD thesis, for which he received the Turing Award in 1988. It helped change the way people interact with computers...
created by Ivan Sutherland
Ivan Sutherland
Ivan Edward Sutherland is an American computer scientist and Internet pioneer. He received the Turing Award from the Association for Computing Machinery in 1988 for the invention of Sketchpad, an early predecessor to the sort of graphical user interface that has become ubiquitous in personal...
in 1960-61; in the glossary of the 1963 technical report based on his dissertation about Sketchpad, Sutherland defined notions of "object" and "instance" (with the class concept covered by "master" or "definition"), albeit specialized to graphical interaction.
Also, an MIT ALGOL
ALGOL
ALGOL is a family of imperative computer programming languages originally developed in the mid 1950s which greatly influenced many other languages and became the de facto way algorithms were described in textbooks and academic works for almost the next 30 years...
version, AED-0, linked data structures ("plexes", in that dialect) directly with procedures, prefiguring what were later termed "messages", "methods" and "member functions".
Objects as a formal concept in programming were introduced in the 1960s in Simula
Simula
Simula is a name for two programming languages, Simula I and Simula 67, developed in the 1960s at the Norwegian Computing Center in Oslo, by Ole-Johan Dahl and Kristen Nygaard...
67, a major revision of Simula I, a programming language designed for discrete event simulation
Discrete Event Simulation
In discrete-event simulation, the operation of a system is represented as a chronological sequence of events. Each event occurs at an instant in time and marks a change of state in the system...
, created by Ole-Johan Dahl
Ole-Johan Dahl
Ole-Johan Dahl was a Norwegian computer scientist and is considered to be one of the fathers of Simula and object-oriented programming along with Kristen Nygaard.- Career :...
and Kristen Nygaard
Kristen Nygaard
Kristen Nygaard was a Norwegian computer scientist, programming language pioneer and politician. He was born in Oslo and died of a heart attack in 2002.-Object-oriented programming:...
of the Norwegian Computing Center
Norwegian Computing Center
Norwegian Computing Center is a private, independent, non-profit research foundation founded in 1952. NR carries out contract research and development in the areas of computing and quantitative methods for a broad range of industrial, commercial and public service organisations in the national...
in Oslo
Oslo
Oslo is a municipality, as well as the capital and most populous city in Norway. As a municipality , it was established on 1 January 1838. Founded around 1048 by King Harald III of Norway, the city was largely destroyed by fire in 1624. The city was moved under the reign of Denmark–Norway's King...
.
Simula 67 was influenced by SIMSCRIPT
SIMSCRIPT
SIMSCRIPT is a free-form, English-like general-purpose simulation language conceived by Harry Markowitz and Bernard Hausner at the RAND Corporation in 1963. It was implemented as a Fortran preprocessor on the IBM 7090 and was designed for large discrete event simulations...
and Hoare's proposed "record classes".
Simula introduced the notion of classes and instances or objects (as well as subclasses, virtual methods, coroutines, and discrete event simulation) as part of an explicit programming paradigm. The language also used automatic garbage collection
Garbage collection (computer science)
In computer science, garbage collection is a form of automatic memory management. The garbage collector, or just collector, attempts to reclaim garbage, or memory occupied by objects that are no longer in use by the program...
that had been invented earlier for the functional programming
Functional programming
In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state...
language Lisp. Simula was used for physical modeling, such as models to study and improve the movement of ships and their content through cargo ports. The ideas of Simula 67 influenced many later languages, including Smalltalk, derivatives of LISP (CLOS
CLOS
The Common Lisp Object System is the facility for object-oriented programming which is part of ANSI Common Lisp. CLOS is a powerful dynamic object system which differs radically from the OOP facilities found in more static languages such as C++ or Java. CLOS was inspired by earlier Lisp object...
), Object Pascal
Object Pascal
Object Pascal refers to a branch of object-oriented derivatives of Pascal, mostly known as the primary programming language of Embarcadero Delphi.-Early history at Apple:...
, and C++
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
.
The Smalltalk
Smalltalk
Smalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis." It was designed and created in part for educational use, more so for constructionist...
language, which was developed at Xerox PARC
Xerox PARC
PARC , formerly Xerox PARC, is a research and co-development company in Palo Alto, California, with a distinguished reputation for its contributions to information technology and hardware systems....
(by Alan Kay
Alan Kay
Alan Curtis Kay is an American computer scientist, known for his early pioneering work on object-oriented programming and windowing graphical user interface design, and for coining the phrase, "The best way to predict the future is to invent it."He is the president of the Viewpoints Research...
and others) in the 1970s, introduced the term object-oriented programming to represent the pervasive use of objects and messages as the basis for computation. Smalltalk creators were influenced by the ideas introduced in Simula 67, but Smalltalk was designed to be a fully dynamic system in which classes could be created and modified dynamically rather than statically as in Simula 67. Smalltalk and with it OOP were introduced to a wider audience by the August 1981 issue of Byte Magazine
Byte (magazine)
BYTE magazine was a microcomputer magazine, influential in the late 1970s and throughout the 1980s because of its wide-ranging editorial coverage...
.
In the 1970s, Kay's Smalltalk work had influenced the Lisp community to incorporate object-based techniques that were introduced to developers via the Lisp machine
Lisp machine
Lisp machines were general-purpose computers designed to efficiently run Lisp as their main software language. In a sense, they were the first commercial single-user workstations...
. Experimentation with various extensions to Lisp (like LOOPS and Flavors introducing multiple inheritance
Multiple inheritance
Multiple inheritance is a feature of some object-oriented computer programming languages in which a class can inherit behaviors and features from more than one superclass....
and mixins), eventually led to the Common Lisp Object System (CLOS, a part of the first standardized object-oriented programming language, ANSI
Ansi
Ansi is a village in Kaarma Parish, Saare County, on the island of Saaremaa, Estonia....
Common Lisp
Common Lisp
Common Lisp, commonly abbreviated CL, is a dialect of the Lisp programming language, published in ANSI standard document ANSI INCITS 226-1994 , . From the ANSI Common Lisp standard the Common Lisp HyperSpec has been derived for use with web browsers...
), which integrates functional programming and object-oriented programming and allows extension via a Meta-object protocol. In the 1980s, there were a few attempts to design processor architectures that included hardware support for objects in memory but these were not successful. Examples include the Intel iAPX 432
Intel iAPX 432
The Intel iAPX 432 was a commercially unsuccessful 32-bit microprocessor architecture, introduced in 1981.The project was Intel's first 32-bit microprocessor design, and intended to be the company's main product line for the 1980s. Many advanced multitasking and memory management features were...
and the Linn Smart
Linn Products
Linn Products is a Scottish company, based in Glasgow, that manufactures hi-fi audio equipment, home theatre, and multi-room integrated audio systems...
Rekursiv
Rekursiv
Rekursiv was a computer processor designed by David M. Harland in the mid-1980s for Linn Smart Computing in Glasgow, Scotland. It was one of the few computer architectures intended to implement object-oriented concepts directly in hardware. The Rekursiv operated directly on objects rather than...
.
Object-oriented programming developed as the dominant programming methodology in the early and mid 1990s when programming languages supporting the techniques became widely available. These included Visual FoxPro 3.0, C++
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
, and Delphi. Its dominance was further enhanced by the rising popularity of graphical user interface
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
s, which rely heavily upon object-oriented programming techniques. An example of a closely related dynamic GUI library and OOP language can be found in the Cocoa frameworks on Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, written in Objective-C
Objective-C
Objective-C is a reflective, object-oriented programming language that adds Smalltalk-style messaging to the C programming language.Today, it is used primarily on Apple's Mac OS X and iOS: two environments derived from the OpenStep standard, though not compliant with it...
, an object-oriented, dynamic messaging extension to C based on Smalltalk. OOP toolkits also enhanced the popularity of event-driven programming
Event-driven programming
In computer programming, event-driven programming or event-based programming is a programming paradigm in which the flow of the program is determined by events—i.e., sensor outputs or user actions or messages from other programs or threads.Event-driven programming can also be defined as an...
(although this concept is not limited to OOP). Some feel that association with GUIs (real or perceived) was what propelled OOP into the programming mainstream.
At ETH Zürich
ETH Zurich
The Swiss Federal Institute of Technology Zurich or ETH Zürich is an engineering, science, technology, mathematics and management university in the City of Zurich, Switzerland....
, Niklaus Wirth
Niklaus Wirth
Niklaus Emil Wirth is a Swiss computer scientist, best known for designing several programming languages, including Pascal, and for pioneering several classic topics in software engineering. In 1984 he won the Turing Award for developing a sequence of innovative computer languages.-Biography:Wirth...
and his colleagues had also been investigating such topics as data abstraction and modular programming
Modularity (programming)
Modular programming is a software design technique that increases the extent to which software is composed of separate, interchangeable components called modules by breaking down program functions into modules, each of which accomplishes one function and contains everything necessary to accomplish...
(although this had been in common use in the 1960s or earlier). Modula-2
Modula-2
Modula-2 is a computer programming language designed and developed between 1977 and 1980 by Niklaus Wirth at ETH Zurich as a revision of Pascal to serve as the sole programming language for the operating system and application software for the personal workstation Lilith...
(1978) included both, and their succeeding design, Oberon
Oberon (programming language)
Oberon is a programming language created in 1986 by Professor Niklaus Wirth and his associates at ETH Zurich in Switzerland. It was developed as part of the implementation of the Oberon operating system...
, included a distinctive approach to object orientation, classes, and such. The approach is unlike Smalltalk, and very unlike C++.
Object-oriented features have been added to many existing languages during that time, including Ada
Ada (programming language)
Ada is a structured, statically typed, imperative, wide-spectrum, and object-oriented high-level computer programming language, extended from Pascal and other languages...
, BASIC
BASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
, Fortran
Fortran
Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
, Pascal
Pascal (programming language)
Pascal is an influential imperative and procedural programming language, designed in 1968/9 and published in 1970 by Niklaus Wirth as a small and efficient language intended to encourage good programming practices using structured programming and data structuring.A derivative known as Object Pascal...
, and others. Adding these features to languages that were not initially designed for them often led to problems with compatibility and maintainability of code.
More recently, a number of languages have emerged that are primarily object-oriented yet compatible with procedural methodology, such as Python
Python (programming language)
Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
and Ruby. Probably the most commercially important recent object-oriented languages are Visual Basic.NET (VB.NET) and C#, both designed for Microsoft's .NET
.NET Framework
The .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and supports several programming languages which allows language interoperability...
platform, and Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
, developed by Sun Microsystems
Sun Microsystems
Sun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982...
. Both frameworks show the benefit of using OOP by creating an abstraction from implementation in their own way. VB.NET and C# support cross-language inheritance, allowing classes defined in one language to subclass classes defined in the other language. Developers usually compile Java to bytecode
Bytecode
Bytecode, also known as p-code , is a term which has been used to denote various forms of instruction sets designed for efficient execution by a software interpreter as well as being suitable for further compilation into machine code...
, allowing Java to run on any operating system for which a Java virtual machine
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
is available. VB.NET and C# make use of the Strategy pattern
Strategy pattern
In computer programming, the strategy pattern is a particular software design pattern, whereby algorithms can be selected at runtime. Formally speaking, the strategy pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable...
to accomplish cross-language inheritance, whereas Java makes use of the Adapter pattern
Adapter pattern
In computer programming, the adapter pattern is a design pattern that translates one interface for a class into a compatible interface...
.
Just as procedural programming
Procedural programming
Procedural programming can sometimes be used as a synonym for imperative programming , but can also refer to a programming paradigm, derived from structured programming, based upon the concept of the procedure call...
led to refinements of techniques such as structured programming
Structured programming
Structured programming is a programming paradigm aimed on improving the clarity, quality, and development time of a computer program by making extensive use of subroutines, block structures and for and while loops - in contrast to using simple tests and jumps such as the goto statement which could...
, modern object-oriented software design methods include refinements such as the use of design patterns
Design pattern (computer science)
In software engineering, a design pattern is a general reusable solution to a commonly occurring problem within a given context in software design. A design pattern is not a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that...
, design by contract
Design by contract
Design by contract , also known as programming by contract and design-by-contract programming, is an approach to designing computer software...
, and modeling language
Modeling language
A modeling language is any artificial language that can be used to express information or knowledge or systems in a structure that is defined by a consistent set of rules...
s (such as UML
Unified Modeling Language
Unified Modeling Language is a standardized general-purpose modeling language in the field of object-oriented software engineering. The standard is managed, and was created, by the Object Management Group...
).
Fundamental features and concepts
A survey by Deborah J. Armstrong of nearly 40 years of computing literature identified a number of "quarks", or fundamental concepts, found in the strong majority of definitions of OOP.Not all of these concepts are to be found in all object-oriented programming languages. For example, object-oriented programming that uses classes is sometimes called class-based programming
Class-based programming
Class-based programming, or more commonly class-orientation, refers to the style of object-oriented programming in which inheritance is achieved by defining classes of objects, as opposed to the objects themselves .The most popular and developed model of OOP is a class-based model, as opposed to an...
, while prototype-based programming
Prototype-based programming
Prototype-based programming is a style of object-oriented programming in which classes are not present, and behavior reuse is performed via a process of cloning existing objects that serve as prototypes. This model can also be known as classless, prototype-oriented or instance-based programming...
does not typically use classes. As a result, a significantly different yet analogous terminology is used to define the concepts of object and instance.
Benjamin C. Pierce and some other researchers view as futile any attempt to distill OOP to a minimal set of features. He nonetheless identifies fundamental features that support the OOP programming style in most object-oriented languages:
- Dynamic dispatchDynamic dispatchIn computer science, dynamic dispatch is the process of mapping a message to a specific sequence of code at runtime. This is done to support the cases where the appropriate method can't be determined at compile-time...
– when a method is invoked on an object, the object itself determines what code gets executed by looking up the method at run time in a table associated with the object. This feature distinguishes an object from an abstract data typeAbstract data typeIn computing, an abstract data type is a mathematical model for a certain class of data structures that have similar behavior; or for certain data types of one or more programming languages that have similar semantics...
(or module), which has a fixed (static) implementation of the operations for all instances. It is a programming methodology that gives modular component development while at the same time being very efficient. - EncapsulationEncapsulation (object-oriented programming)In a programming language encapsulation is used to refer to one of two related but distinct notions, and sometimes to the combination thereof:* A language mechanism for restricting access to some of the object's components....
(or multi-methods, in which case the state is kept separate) - Subtype polymorphismSubtype polymorphismIn programming language theory, subtyping or subtype polymorphism is a form of type polymorphism in which a subtype is a datatype that is related to another datatype by some notion of substitutability, meaning that program constructs, typically subroutines or functions, written to operate on...
- Object inheritanceInheritance (object-oriented programming)In object-oriented programming , inheritance is a way to reuse code of existing objects, establish a subtype from an existing object, or both, depending upon programming language support...
(or delegation) - Open recursion – a special variable (syntactically it may be a keyword), usually called
thisorself, that allows a method body to invoke another method body of the same object. This variable is late-boundName bindingIn programming languages, name binding is the association of objects with identifiers. An identifier bound to an object is said to reference that object. Machine languages have no built-in notion of identifiers, but name-object bindings as a service and notation for the programmer is implemented...
; it allows a method defined in one class to invoke another method that is defined later, in some subclass thereof.
Similarly, in his 2003 book, Concepts in programming languages, John C. Mitchell identifies four main features: dynamic dispatch, abstraction
Abstraction (computer science)
In computer science, abstraction is the process by which data and programs are defined with a representation similar to its pictorial meaning as rooted in the more complex realm of human life and language with their higher need of summarization and categorization , while hiding away the...
, subtype polymorphism, and inheritance. Michael Lee Scott in Programming Language Pragmatics considers only encapsulation, inheritance and dynamic dispatch.
Additional concepts used in object-oriented programming include:
- ClassClass (computer science)In object-oriented programming, a class is a construct that is used as a blueprint to create instances of itself – referred to as class instances, class objects, instance objects or simply objects. A class defines constituent members which enable these class instances to have state and behavior...
es of objects - InstanceInstance (computer science)In object-oriented programming an instance is an occurrence or a copy of an object, whether currently executing or not. Instances of a class share the same set of attributes, yet will typically differ in what those attributes contain....
s of classes - MethodMethod (computer science)In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...
s which act on the attached objects. - Message passingMessage passingMessage passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes...
- AbstractionAbstraction (computer science)In computer science, abstraction is the process by which data and programs are defined with a representation similar to its pictorial meaning as rooted in the more complex realm of human life and language with their higher need of summarization and categorization , while hiding away the...
Decoupling
Decoupling refers to careful controls that separate code modules from particular use cases, which increases code re-usability. A common use of decoupling in OOP is to polymorphically decouple the encapsulation (see Bridge patternBridge pattern
The bridge pattern is a design pattern used in software engineering which is meant to "decouple an abstraction from its implementation so that the two can vary independently"...
and Adapter pattern
Adapter pattern
In computer programming, the adapter pattern is a design pattern that translates one interface for a class into a compatible interface...
) - for example, using a method interface which an encapsulated object must satisfy, as opposed to using the object's class.
Formal semantics
There have been several attempts at formalizing the concepts used in object-oriented programming. The following concepts and constructs have been used as interpretations of OOP concepts:- coalgebraic data typesF-coalgebraIn mathematics, specifically in category theory, an F-coalgebra is a structure defined according to a functor F. For both algebra and coalgebra, a functor is a convenient and general way of organizing a signature...
- abstract data typeAbstract data typeIn computing, an abstract data type is a mathematical model for a certain class of data structures that have similar behavior; or for certain data types of one or more programming languages that have similar semantics...
s (which have existential types) allow the definition of modules but these do not support dynamic dispatchDynamic dispatchIn computer science, dynamic dispatch is the process of mapping a message to a specific sequence of code at runtime. This is done to support the cases where the appropriate method can't be determined at compile-time... - recursive typeRecursive typeIn computer programming languages, a recursive data type is a data type for values that may contain other values of the same type...
s - encapsulated state
- Inheritance (object-oriented programming)Inheritance (object-oriented programming)In object-oriented programming , inheritance is a way to reuse code of existing objects, establish a subtype from an existing object, or both, depending upon programming language support...
- recordsRecord (computer science)In computer science, a record is an instance of a product of primitive data types called a tuple. In C it is the compound data in a struct. Records are among the simplest data structures. A record is a value that contains other values, typically in fixed number and sequence and typically indexed...
are basis for understanding objects if function literals can be stored in fields (like in functional programming languages), but the actual calculi need be considerably more complex to incorporate essential features of OOP. Several extensions of System F<: that deal with mutable objects have been studied; these allow both subtype polymorphismSubtype polymorphismIn programming language theory, subtyping or subtype polymorphism is a form of type polymorphism in which a subtype is a datatype that is related to another datatype by some notion of substitutability, meaning that program constructs, typically subroutines or functions, written to operate on...
and parametric polymorphismParametric polymorphismIn programming languages and type theory, parametric polymorphism is a way to make a language more expressive, while still maintaining full static type-safety. Using parametric polymorphism, a function or a data type can be written generically so that it can handle values identically without...
(generics)
Attempts to find a consensus definition or theory behind objects have not proven very successful (however, see Abadi & Cardelli, A Theory of Objects for formal definitions of many OOP concepts and constructs), and often diverge widely. For example, some definitions focus on mental activities, and some on program structuring. One of the simpler definitions is that OOP is the act of using "map" data structures or arrays that can contain functions and pointers to other maps, all with some syntactic and scoping sugar on top. Inheritance can be performed by cloning the maps (sometimes called "prototyping").
OBJECT:=>>
Objects are the run time entities in an object-oriented system. They may represent a person, a place, a bank account, a table of data or any item that the program has to handle.
OOP languages
SimulaSimula
Simula is a name for two programming languages, Simula I and Simula 67, developed in the 1960s at the Norwegian Computing Center in Oslo, by Ole-Johan Dahl and Kristen Nygaard...
(1967) is generally accepted as the first language to have the primary features of an object-oriented language. It was created for making simulation program
Computer simulation
A computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system...
s, in which what came to be called objects were the most important information representation. Smalltalk
Smalltalk
Smalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis." It was designed and created in part for educational use, more so for constructionist...
(1972 to 1980) is arguably the canonical example, and the one with which much of the theory of object-oriented programming was developed. Concerning the degree of object orientation, following distinction can be made:
- Languages called "pure" OO languages, because everything in them is treated consistently as an object, from primitives such as characters and punctuation, all the way up to whole classes, prototypes, blocks, modules, etc. They were designed specifically to facilitate, even enforce, OO methods. Examples: [programming language)|Scala]], SmalltalkSmalltalkSmalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis." It was designed and created in part for educational use, more so for constructionist...
, EiffelEiffel (programming language)Eiffel is an ISO-standardized, object-oriented programming language designed by Bertrand Meyer and Eiffel Software. The design of the language is closely connected with the Eiffel programming method...
, RubyRuby (programming language)Ruby is a dynamic, reflective, general-purpose object-oriented programming language that combines syntax inspired by Perl with Smalltalk-like features. Ruby originated in Japan during the mid-1990s and was first developed and designed by Yukihiro "Matz" Matsumoto...
, JADE, EmeraldEmerald (programming language)Emerald is a distributed, object-oriented programming language developed in the 1980s by Andrew P. Black, Norman C. Hutchinson, Eric Jul, and Henry M...
. - Languages designed mainly for OO programming, but with some procedural elements. Examples: C++C++C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
, C#, VB.NET, JavaJava (programming language)Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
, PythonPython (programming language)Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
. (Note: C# and VB.NETComparison of C sharp and Visual Basic .NETC# and Visual Basic .NET are the two primary languages used to program on the .NET Framework.-Language history:C# and VB.NET are syntactically very different languages with very different history...
are both exclusively part of Microsoft's .NET Framework development platform and compile to the same intermediate language (IL). Although there are some construct differences, they are minimal and in the context of this grouping, some might consider them part of one language with simply two syntax translation engines). - Languages that are historically procedural languagesProcedural programmingProcedural programming can sometimes be used as a synonym for imperative programming , but can also refer to a programming paradigm, derived from structured programming, based upon the concept of the procedure call...
, but have been extended with some OO features. Examples: Visual BasicVisual BasicVisual Basic is the third-generation event-driven programming language and integrated development environment from Microsoft for its COM programming model...
(derived from BASIC), Fortran 2003, PerlPerlPerl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
, COBOLCOBOLCOBOL is one of the oldest programming languages. Its name is an acronym for COmmon Business-Oriented Language, defining its primary domain in business, finance, and administrative systems for companies and governments....
2002, PHPPHPPHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document...
, ABAPABAPABAP , is a high-level programming language created by the German software company SAP...
. - Languages with most of the features of objects (classes, methods, inheritance, reusability), but in a distinctly original form. Examples: OberonOberon (programming language)Oberon is a programming language created in 1986 by Professor Niklaus Wirth and his associates at ETH Zurich in Switzerland. It was developed as part of the implementation of the Oberon operating system...
(Oberon-1 or Oberon-2) and Common LispCommon LispCommon Lisp, commonly abbreviated CL, is a dialect of the Lisp programming language, published in ANSI standard document ANSI INCITS 226-1994 , . From the ANSI Common Lisp standard the Common Lisp HyperSpec has been derived for use with web browsers...
. - Languages with abstract data typeAbstract data typeIn computing, an abstract data type is a mathematical model for a certain class of data structures that have similar behavior; or for certain data types of one or more programming languages that have similar semantics...
support, but not all features of object-orientation, sometimes called object-based languages. Examples: Modula-2Modula-2Modula-2 is a computer programming language designed and developed between 1977 and 1980 by Niklaus Wirth at ETH Zurich as a revision of Pascal to serve as the sole programming language for the operating system and application software for the personal workstation Lilith...
(with excellent encapsulation and information hiding), Pliant, CLU.
OOP in dynamic languages
In recent years, object-oriented programming has become especially popular in dynamic programming languageDynamic programming language
Dynamic programming language is a term used broadly in computer science to describe a class of high-level programming languages that execute at runtime many common behaviors that other languages might perform during compilation, if at all...
s. Python
Python (programming language)
Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
, Ruby
Ruby (programming language)
Ruby is a dynamic, reflective, general-purpose object-oriented programming language that combines syntax inspired by Perl with Smalltalk-like features. Ruby originated in Japan during the mid-1990s and was first developed and designed by Yukihiro "Matz" Matsumoto...
and Groovy are dynamic languages built on OOP principles, while Perl
Perl
Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
and PHP
PHP
PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document...
have been adding object oriented features since Perl 5 and PHP 4, and ColdFusion
ColdFusion
In computing, ColdFusion is the name of a commercial rapid application development platform invented by Jeremy and JJ Allaire in 1995. ColdFusion was originally designed to make it easier to connect simple HTML pages to a database, by version 2 it had...
since version 5.
The Document Object Model
Document Object Model
The Document Object Model is a cross-platform and language-independent convention for representing and interacting with objects in HTML, XHTML and XML documents. Aspects of the DOM may be addressed and manipulated within the syntax of the programming language in use...
of HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....
, XHTML
XHTML
XHTML is a family of XML markup languages that mirror or extend versions of the widely-used Hypertext Markup Language , the language in which web pages are written....
, and XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
documents on the Internet have bindings to the popular JavaScript
JavaScript
JavaScript is a prototype-based scripting language that is dynamic, weakly typed and has first-class functions. It is a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles....
/ECMAScript
ECMAScript
ECMAScript is the scripting language standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side scripting on the web, in the form of several well-known dialects such as JavaScript, JScript, and ActionScript.- History :JavaScript...
language. JavaScript is perhaps the best known prototype-based programming
Prototype-based programming
Prototype-based programming is a style of object-oriented programming in which classes are not present, and behavior reuse is performed via a process of cloning existing objects that serve as prototypes. This model can also be known as classless, prototype-oriented or instance-based programming...
language, which employs cloning from prototypes rather than inheriting from a class. Another scripting language that takes this approach is Lua. Earlier versions of ActionScript
ActionScript
ActionScript is an object-oriented language originally developed by Macromedia Inc. . It is a dialect of ECMAScript , and is used primarily for the development of websites and software targeting the Adobe Flash Player platform, used on Web pages in the form of...
(a partial superset of the ECMA-262 R3, otherwise known as ECMAScript) also used a prototype-based object model. Later versions of ActionScript incorporate a combination of classification and prototype-based object models based largely on the currently incomplete ECMA-262 R4 specification, which has its roots in an early JavaScript 2 Proposal. Microsoft's JScript.NET also includes a mash-up of object models based on the same proposal, and is also a superset of the ECMA-262 R3 specification.
Design Patterns
Challenges of object-oriented design are addressed by several methodologies. Most common is known as the design patterns codified by Gamma et al.. More broadly, the term "design patternsDesign pattern (computer science)
In software engineering, a design pattern is a general reusable solution to a commonly occurring problem within a given context in software design. A design pattern is not a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that...
" can be used to refer to any general, repeatable solution to a commonly occurring problem in software design. Some of these commonly occurring problems have implications and solutions particular to object-oriented development.
Inheritance and behavioral subtyping
It is intuitive to assume that inheritance creates a semantic "is a" relationship, and thus to infer that objects instantiated from subclasses can always be safely used instead of those instantiated from the superclass. This intuition is unfortunately false in most OOP languages, in particular in all those that allow mutable objects. Subtype polymorphismSubtype polymorphism
In programming language theory, subtyping or subtype polymorphism is a form of type polymorphism in which a subtype is a datatype that is related to another datatype by some notion of substitutability, meaning that program constructs, typically subroutines or functions, written to operate on...
as enforced by the type checker in OOP languages (with mutable objects) cannot guarantee behavioral subtyping in any context. Behavioral subtyping is undecidable in general, so it cannot be implemented by a program (compiler). Class or object hierarchies need to be carefully designed considering possible incorrect uses that cannot be detected syntactically. This issue is known as the Liskov substitution principle
Liskov substitution principle
Substitutability is a principle in object-oriented programming. It states that, in a computer program, if S is a subtype of T, then objects of type T may be replaced with objects of type S without altering any of the desirable properties of that program...
.
Gang of Four design patterns
Design Patterns: Elements of Reusable Object-Oriented Software is an influential book published in 1995 by Erich GammaErich Gamma
Erich Gamma is Swiss computer scientist and co-author of the influential Software engineering textbook, Design Patterns: Elements of Reusable Object-Oriented Software. He co-wrote the JUnit software testing framework with Kent Beck and led the design of the Eclipse platform's Java Development Tools...
, Richard Helm, Ralph Johnson, and John Vlissides
John Vlissides
John Matthew Vlissides was a software scientist known mainly as one of the four authors of the book Design Patterns: Elements of Reusable Object-Oriented Software...
, sometimes casually called the "Gang of Four". Along with exploring the capabilities and pitfalls of object-oriented programming, it describes 23 common programming problems and patterns for solving them.
As of April 2007, the book was in its 36th printing.
The book describes the following patterns:
- Creational patternCreational patternIn software engineering, creational design patterns are design patterns that deal with object creation mechanisms, trying to create objects in a manner suitable to the situation. The basic form of object creation could result in design problems or added complexity to the design. Creational design...
s (5): Factory method patternFactory method patternThe factory method pattern is an object-oriented design pattern to implement the concept of factories. Like other creational patterns, it deals with the problem of creating objects without specifying the exact class of object that will be created.The creation of an object often requires complex...
, Abstract factory patternAbstract factory patternThe abstract factory pattern is a software design pattern that provides a way to encapsulate a group of individual factories that have a common theme. In normal usage, the client software creates a concrete implementation of the abstract factory and then uses the generic interfaces to create the...
, Singleton patternSingleton patternIn software engineering, the singleton pattern is a design pattern used to implement the mathematical concept of a singleton, by restricting the instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system...
, Builder patternBuilder patternThe builder pattern is an object creation software design pattern. The intention is to abstract steps of construction of objects so that different implementations of these steps can construct different representations of objects...
, Prototype patternPrototype patternThe prototype pattern is a creational design pattern used in software development when the type of objects to create is determined by a prototypical instance, which is cloned to produce new objects... - Structural patternStructural patternIn software engineering, structural design patterns are design patterns that ease the design by identifying a simple way to realize relationships between entities.Examples of Structural Patterns include:...
s (7): Adapter patternAdapter patternIn computer programming, the adapter pattern is a design pattern that translates one interface for a class into a compatible interface...
, Bridge patternBridge patternThe bridge pattern is a design pattern used in software engineering which is meant to "decouple an abstraction from its implementation so that the two can vary independently"...
, Composite patternComposite patternIn software engineering, the composite pattern is a partitioning design pattern. The composite pattern describes that a group of objects are to be treated in the same way as a single instance of an object. The intent of a composite is to "compose" objects into tree structures to represent...
, Decorator patternDecorator patternIn object-oriented programming, the decorator pattern is a design pattern that allows behaviour to be added to an existing object dynamically.-Introduction:...
, Facade patternFaçade patternThe facade pattern is a software engineering design pattern commonly used with Object-oriented programming. The name is by analogy to an architectural facade....
, Flyweight patternFlyweight patternFlyweight is a software design pattern. A flyweight is an object that minimizes memory use by sharing as much data as possible with other similar objects; it is a way to use objects in large numbers when a simple repeated representation would use an unacceptable amount of memory. The term is named...
, Proxy patternProxy patternIn computer programming, the proxy pattern is a software design pattern.A proxy, in its most general form, is a class functioning as an interface to something else... - Behavioral patternBehavioral patternIn software engineering, behavioral design patterns are design patterns that identify common communication patterns between objects and realize these patterns...
s (11): Chain-of-responsibility patternChain-of-responsibility patternIn Object Oriented Design, the chain-of-responsibility pattern is a design pattern consisting of a source of command objects and a series of processing objects. Each processing object contains a set of logic that describes the types of command objects that it can handle, and how to pass off those...
, Command patternCommand patternIn object-oriented programming, the command pattern is a design pattern in which an object is used to represent and encapsulate all the information needed to call a method at a later time...
, Interpreter patternInterpreter patternIn computer programming, the interpreter pattern is a design pattern. The interpreter pattern specifies how to evaluate sentences in a language. The basic idea is to have a class for each symbol in a specialized computer language...
, Iterator patternIterator patternIn object-oriented programming, the iterator pattern is a design pattern in which an iterator is used to traverse a container and access the container's elements...
, Mediator patternMediator patternThe mediator pattern, one of the 23 design patterns described in Design Patterns: Elements of Reusable Object-Oriented Software, provides a unified interface to a set of interfaces in a subsystem. This pattern is considered to be a behavioral pattern due to the way it can alter the program's...
, Memento patternMemento patternThe memento pattern is a software design pattern that provides the ability to restore an object to its previous state .The memento pattern is implemented with two objects: the originator and a caretaker. The originator is some object that has an internal state. The caretaker is going to do...
, Observer patternObserver patternThe observer pattern is a software design pattern in which an object, called the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods...
, State patternState patternThe state pattern, which closely resembles Strategy Pattern, is a behavioral software design pattern, also known as the objects for states pattern. This pattern is used in computer programming to represent the state of an object. This is a clean way for an object to partially change its type at...
, Strategy patternStrategy patternIn computer programming, the strategy pattern is a particular software design pattern, whereby algorithms can be selected at runtime. Formally speaking, the strategy pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable...
, Template method patternTemplate method patternIn software engineering, the template method pattern is a design pattern.It is a behavioral pattern, and is unrelated to C++ templates.-Introduction:A template method defines the program skeleton of an algorithm...
, Visitor patternVisitor patternIn object-oriented programming and software engineering, the visitor design pattern is a way of separating an algorithm from an object structure on which it operates. A practical result of this separation is the ability to add new operations to existing object structures without modifying those...
Object-orientation and databases
Both object-oriented programming and relational database management systems (RDBMSs) are extremely common in software . Since relational databaseRelational database
A relational database is a database that conforms to relational model theory. The software used in a relational database is called a relational database management system . Colloquial use of the term "relational database" may refer to the RDBMS software, or the relational database itself...
s don't store objects directly (though some RDBMSs have object-oriented features to approximate this), there is a general need to bridge the two worlds. The problem of bridging object-oriented programming accesses and data patterns with relational databases is known as Object-Relational impedance mismatch
Object-Relational impedance mismatch
The object-relational impedance mismatch is a set of conceptual and technical difficulties that are often encountered when a relational database management system is being used by a program written in an object-oriented programming language or style; particularly when objects or class definitions...
. There are a number of approaches to cope with this problem, but no general solution without downsides. One of the most common approaches is object-relational mapping
Object-relational mapping
Object-relational mapping in computer software is a programming technique for converting data between incompatible type systems in object-oriented programming languages. This creates, in effect, a "virtual object database" that can be used from within the programming language...
, as found in libraries like Java Data Objects
Java Data Objects
Java Data Objects is a specification of Java object persistence. One of its features is a transparency of the persistent services to the domain model. JDO persistent objects are ordinary Java programming language classes ; there's no requirement for them to implement certain interfaces or extend...
and Ruby on Rails
Ruby on Rails
Ruby on Rails, often shortened to Rails or RoR, is an open source web application framework for the Ruby programming language.-History:...
' ActiveRecord.
There are also object database
Object database
An object database is a database management system in which information is represented in the form of objects as used in object-oriented programming...
s that can be used to replace RDBMSs, but these have not been as technically and commercially successful as RDBMSs.
Real-world Modeling and Relationships
OOP can be used to associate real-world objects and processes with digital counterparts. However, not everyone agrees that OOP facilitates direct real-world mapping (see Negative Criticism section) or that real-world mapping is even a worthy goal; Bertrand MeyerBertrand Meyer
Bertrand Meyer is an academic, author, and consultant in the field of computer languages. He created the Eiffel programming language.-Education and academic career:...
argues in Object-Oriented Software Construction
Object-Oriented Software Construction
Object-Oriented Software Construction is a book by Bertrand Meyer, widely considered a foundational text of object-oriented programming. The first edition was published in 1988; the second, extensively revised and expanded edition , in 1997...
that a program is not a model of the world but a model of some part of the world; "Reality is a cousin twice removed". At the same time, some principal limitations of OOP had been noted.
For example, the Circle-ellipse problem
Circle-ellipse problem
The circle-ellipse problem in software development illustrates a number of pitfalls which can arise when using subtype polymorphism in object modelling...
is difficult to handle using OOP's concept of inheritance
Inheritance (object-oriented programming)
In object-oriented programming , inheritance is a way to reuse code of existing objects, establish a subtype from an existing object, or both, depending upon programming language support...
.
However, Niklaus Wirth
Niklaus Wirth
Niklaus Emil Wirth is a Swiss computer scientist, best known for designing several programming languages, including Pascal, and for pioneering several classic topics in software engineering. In 1984 he won the Turing Award for developing a sequence of innovative computer languages.-Biography:Wirth...
(who popularized the adage now known as Wirth's law
Wirth's law
Wirth's law is a computing adage made popular by Niklaus Wirth in 1995:Wirth attributed the saying to Martin Reiser, who, in the preface to his book on the Oberon System, wrote: The hope is that the progress in hardware will cure all software ills...
: "Software is getting slower more rapidly than hardware becomes faster") said of OOP in his paper, "Good Ideas through the Looking Glass", "This paradigm closely reflects the structure of systems 'in the real world', and it is therefore well suited to model complex systems with complex behaviours" (contrast KISS principle
KISS principle
KISS is an acronym for the design principle Keep it simple, Stupid!. Other variations include "keep it simple and stupid", "keep it short and simple", "keep it simple sir", "keep it simple or be stupid" or "keep it simple and straightforward"...
).
Steve Yegge
Steve Yegge
Steve Yegge is a programmer and blogger who is known for writing about "programming languages, productivity and software culture". He received a bachelor's degree in computer science from the University of Washington and has two decades of industry experience, developing across domains including...
and others noted that natural languages lack the OOP approach of strictly prioritizing things (objects/noun
Noun
In linguistics, a noun is a member of a large, open lexical category whose members can occur as the main word in the subject of a clause, the object of a verb, or the object of a preposition .Lexical categories are defined in terms of how their members combine with other kinds of...
s) before actions (methods/verb
Verb
A verb, from the Latin verbum meaning word, is a word that in syntax conveys an action , or a state of being . In the usual description of English, the basic form, with or without the particle to, is the infinitive...
s). This problem may cause OOP to suffer more convoluted solutions than procedural programming.
OOP and control flow
OOP was developed to increase the reusabilityCode reuse
Code reuse, also called software reuse, is the use of existing software, or software knowledge, to build new software.-Overview:Ad hoc code reuse has been practiced from the earliest days of programming. Programmers have always reused sections of code, templates, functions, and procedures...
and maintainability
Software maintenance
Software Maintenance in software engineering is the modification of a software product after delivery to correct faults, to improve performance or other attributes....
of source code. Transparent representation of the control flow
Control flow
In computer science, control flow refers to the order in which the individual statements, instructions, or function calls of an imperative or a declarative program are executed or evaluated....
had no priority and was meant to be handled by a compiler. With the increasing relevance of parallel hardware and multithreaded coding
Thread (computer science)
In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process...
, developer transparent control flow becomes more important, something hard to achieve with OOP.
Responsibility- vs. data-driven design
Responsibility-driven designResponsibility-driven design
Responsibility-driven design is a design technique in Object-oriented programming. It was proposed by Rebecca Wirfs-Brock and Brian Wilkerson who defined it as follows:Responsibility-driven design is inspired by the client/server model...
defines classes in terms of a contract, that is, a class should be defined around a responsibility and the information that it shares. This is contrasted by Wirfs-Brock and Wilkerson with data-driven design
Data-driven design
In computer programming, data-driven programming is a programming paradigm in which the program statements describe the data to be matched and the processing required rather than defining a sequence of steps to be taken. Adapting abstract data type design methods to object-oriented programming...
, where classes are defined around the data-structures that must be held. The authors hold that responsibility-driven design is preferable.
Criticism
A number of well-known researchers and programmers have analysed the utility of OOP. Here is an incomplete list:- Luca CardelliLuca CardelliLuca Cardelli is an Italian computer scientist who is currently an Assistant Director at Microsoft Research in Cambridge, UK. Cardelli is well-known for his research in type theory and operational semantics. Among other contributions he implemented the first compiler for the functional programming...
wrote a paper titled "Bad Engineering Properties of Object-Oriented Languages". - Richard StallmanRichard StallmanRichard Matthew Stallman , often shortened to rms,"'Richard Stallman' is just my mundane name; you can call me 'rms'"|last= Stallman|first= Richard|date= N.D.|work=Richard Stallman's homepage...
wrote in 1995, "Adding OOP to EmacsEmacsEmacs is a class of text editors, usually characterized by their extensibility. GNU Emacs has over 1,000 commands. It also allows the user to combine these commands into macros to automate work.Development began in the mid-1970s and continues actively...
is not clearly an improvement; I used OOP when working on the Lisp MachineLisp machineLisp machines were general-purpose computers designed to efficiently run Lisp as their main software language. In a sense, they were the first commercial single-user workstations...
window systems, and I disagree with the usual view that it is a superior way to program." - A study by Potok et al. has shown no significant difference in productivity between OOP and procedural approaches.
- Christopher J. DateChristopher J. DateChris Date is an independent author, lecturer, researcher, and consultant, specializing in relational database theory.-Biography:Chris Date attended High Wycombe Royal Grammar School from 1951 to 1958 and received his BA in Mathematics from Cambridge University in 1962. He entered the computer...
stated that critical comparison of OOP to other technologies, relational in particular, is difficult because of lack of an agreed-upon and rigorous definition of OOP. Date and Darwen propose a theoretical foundation on OOP that uses OOP as a kind of customizable type systemData typeIn computer programming, a data type is a classification identifying one of various types of data, such as floating-point, integer, or Boolean, that determines the possible values for that type; the operations that can be done on values of that type; the meaning of the data; and the way values of...
to support RDBMS. - Alexander StepanovAlexander StepanovAlexander Alexandrovich Stepanov is the primary designer and implementer of the C++ Standard Template Library, which he started to develop around 1992 while employed at HP Labs...
suggested that OOP provides a mathematically-limited viewpoint and called it "almost as much of a hoax as Artificial IntelligenceArtificial intelligenceArtificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...
. I have yet to see an interesting piece of code that comes from these OO people. In a sense, I am unfair to AI: I learned a lot of stuff from the MIT AI Lab crowd, they have done some really fundamental work....". - Paul Graham has suggested that the purpose of OOP is to act as a "herding mechanism" that keeps mediocre programmers in mediocre organizations from "doing too much damage". This is at the expense of slowing down productive programmers who know how to use more powerful and more compact techniques.
- Joe Armstrong, the principal inventor of Erlang, is quoted as saying "The problem with object-oriented languages is they've got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle."
- Richard Mansfield, author and former editor of COMPUTE!COMPUTE!Compute! was an American computer magazine that was published from 1979 to 1994, though it can trace its origin to 1978 in Len Lindsay's PET Gazette, one of the first magazines for the Commodore PET computer. In its 1980s heyday Compute! covered all major platforms, and several single-platform...
magazine, states that "like countless other intellectual fads over the years ("relevance", communism, "modernism", and so on—history is littered with them), OOP will be with us until eventually reality asserts itself. But considering how OOP currently pervades both universities and workplaces, OOP may well prove to be a durable delusion. Entire generations of indoctrinated programmers continue to march out of the academy, committed to OOP and nothing but OOP for the rest of their lives." He also is quoted as saying "OOP is to writing a program, what going through airport securityAirport securityAirport security refers to the techniques and methods used in protecting airports and aircraft from crime.Large numbers of people pass through airports. This presents potential targets for terrorism and other forms of crime due to the number of people located in a particular location...
is to flying". - Steve YeggeSteve YeggeSteve Yegge is a programmer and blogger who is known for writing about "programming languages, productivity and software culture". He received a bachelor's degree in computer science from the University of Washington and has two decades of industry experience, developing across domains including...
, making a roundabout comparison with Functional programmingFunctional programmingIn computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state...
, writes, "Object Oriented Programming puts the Nouns first and foremost. Why would you go to such lengths to put one part of speech on a pedestal? Why should one kind of concept take precedence over another? It's not as if OOP has suddenly made verbs less important in the way we actually think. It's a strangely skewed perspective." - Rich Hickey, creator of ClojureClojureClojure |closure]]") is a recent dialect of the Lisp programming language created by Rich Hickey. It is a general-purpose language supporting interactive development that encourages a functional programming style, and simplifies multithreaded programming....
, described object systems as over simplistic models of the real world. He emphasized the inability of OOP to model time properly, which is getting increasingly problematic as software systems become more concurrent. - Carnegie-Mellon University Professor Robert HarperRobert Harper (computer scientist)Robert "Bob" William Harper, Jr. is a computer science professor at Carnegie Mellon University who works in programming language research. He made major contributions to the design of the Standard ML programming language and the LF logical framework....
in March 2011 wrote: "This semester Dan Licata and I are co-teaching a new course on functional programmingFunctional programmingIn computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state...
for first-year prospective CS majors... Object-oriented programming is eliminated entirely from the introductory curriculum, because it is both anti-modular and anti-parallel by its very nature, and hence unsuitable for a modern CS curriculum. A proposed new course on object-oriented design methodology will be offered at the sophomore level for those students who wish to study this topic."
See also
- Aspect-oriented programmingAspect-oriented programmingIn computing, aspect-oriented programming is a programming paradigm which aims to increase modularity by allowing the separation of cross-cutting concerns...
- Circle-ellipse problemCircle-ellipse problemThe circle-ellipse problem in software development illustrates a number of pitfalls which can arise when using subtype polymorphism in object modelling...
- Comparison of programming languages (object-oriented programming)Comparison of programming languages (object-oriented programming)This Comparison of programming languages compares how object-oriented programming languages such as C++, Python, Perl, Java and others manipulate data structures.- Object construction and destruction :- Class declaration :- Fields :- Methods :...
- Comparison of programming paradigmsComparison of programming paradigmsThis article attempts to set out the various similarities and differences between the various programming paradigms as a summary in both graphical and tabular format with links to the separate discussions concerning these similarities and differences in existing Wikipedia articles- Main paradigm...
- Component-based software engineeringComponent-based software engineeringComponent-based software engineering is a branch of software engineering that emphasizes the separation of concerns in respect of the wide-ranging functionality available throughout a given software system...
- Constructor overloading
- CORBAÇorbaChorba , ciorbă , shurpa , shorpo , or sorpa is one of various kinds of soup or stew found in national cuisines across Middle East...
- DCOMDistributed component object modelDistributed Component Object Model is a proprietary Microsoft technology for communication among software components distributed across networked computers. DCOM, which originally was called "Network OLE", extends Microsoft's COM, and provides the communication substrate under Microsoft's COM+...
- Design by contractDesign by contractDesign by contract , also known as programming by contract and design-by-contract programming, is an approach to designing computer software...
- GRASP
- IDEF4IDEF4IDEF4, officially named Integrated DEFinition for Object-Oriented Design, is an object-oriented design modeling language for the design of component-based client/server systems. It has been designed to support smooth transition from the application domain and requirements analysis models to the...
- Interface description languageInterface description languageAn interface description language , or IDL for short, is a specification language used to describe a software component's interface...
- Structured programmingStructured programmingStructured programming is a programming paradigm aimed on improving the clarity, quality, and development time of a computer program by making extensive use of subroutines, block structures and for and while loops - in contrast to using simple tests and jumps such as the goto statement which could...
- Lepus3Lepus3LePUS3 is a language for modelling and visualizing object-oriented programs and design patterns. It is defined as a formal specification language, formulated as an axiomatized subset of First-order predicate logic. A diagram in LePUS3 is also called a Codechart...
- Modular programmingModular programmingModular programming is a software design technique that increases the extent to which software is composed of separate, interchangeable components called modules by breaking down program functions into modules, each of which accomplishes one function and contains everything necessary to accomplish...
- Object association
- Object databaseObject databaseAn object database is a database management system in which information is represented in the form of objects as used in object-oriented programming...
- Object-oriented analysis and designObject-oriented analysis and designObject-oriented analysis and design is a software engineering approach that models a system as a group of interacting objects. Each object represents some entity of interest in the system being modeled, and is characterised by its class, its state , and its behavior...
- Object-relational impedance mismatchObject-Relational impedance mismatchThe object-relational impedance mismatch is a set of conceptual and technical difficulties that are often encountered when a relational database management system is being used by a program written in an object-oriented programming language or style; particularly when objects or class definitions...
(and The Third ManifestoThe Third ManifestoThe Third Manifesto is Christopher J. Date's and Hugh Darwen's proposal for future database management systems, a response to two earlier Manifestos with the same purpose. The theme of the manifestos is how to avoid the 'object-relational impedance mismatch' between object-oriented programming...
) - Object-relational mappingObject-relational mappingObject-relational mapping in computer software is a programming technique for converting data between incompatible type systems in object-oriented programming languages. This creates, in effect, a "virtual object database" that can be used from within the programming language...
- Procedural programmingProcedural programmingProcedural programming can sometimes be used as a synonym for imperative programming , but can also refer to a programming paradigm, derived from structured programming, based upon the concept of the procedure call...
- RefactoringRefactoringCode refactoring is "disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior", undertaken in order to improve some of the nonfunctional attributes of the software....
- SOLID
- System Object Model
- Visual FoxProVisual FoxProVisual FoxPro is a data-centric object-oriented and procedural programming language produced by Microsoft. It is derived from FoxPro which was developed by Fox Software beginning in 1984. Fox Technologies merged with Microsoft in 1992, after which the software acquired further features and the...
- ZZT-oopZZT-oopZZT-oop was an early in-game scripting programming language, designed by Tim Sweeney, for his computer game ZZT. The name stands for ZZT Object Oriented Programming language. The name of the language is a play on ZZ Top, an American rock band.-Overview:...