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6,701 | In the 1970s, the first version of the Smalltalk programming language was developed at Xerox PARC by Alan Kay, Dan Ingalls and Adele Goldberg. Smalltalk-72 included a programming environment and was dynamically typed, and at first was interpreted, not compiled. Smalltalk became noted for its application of object orien... |
6,702 | During the late 1970s and 1980s, object-oriented programming rose to prominence. The Flavors object-oriented Lisp was developed starting 1979, introducing multiple inheritance and mixins. In 1981, Goldberg edited the August issue of Byte Magazine, introducing Smalltalk and object-oriented programming to a wide audience... |
6,703 | In the mid-1980s Objective-C was developed by Brad Cox, who had used Smalltalk at ITT Inc.. Bjarne Stroustrup, who had used Simula for his PhD thesis, created the object-oriented C++. In 1985, Bertrand Meyer also produced the first design of the Eiffel language. Focused on software quality, Eiffel is a purely object-or... |
6,704 | In the early and mid-1990s object-oriented programming developed as the dominant programming paradigm 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 interfaces,... |
6,705 | At ETH Zürich, Niklaus Wirth and his colleagues investigated the concept of type checking across module boundaries. Modula-2 included this concept, and their succeeding design, Oberon, included a distinctive approach to object orientation, classes, and such. Inheritance is not obvious in Wirth's design since his nomen... |
6,706 | Object-oriented features have been added to many previously existing languages, including Ada, BASIC, Fortran, Pascal, and COBOL. Adding these features to languages that were not initially designed for them often led to problems with compatibility and maintainability of code. |
6,707 | More recently, some languages have emerged that are primarily object-oriented, but that are also compatible with procedural methodology. Two such languages are Python and Ruby. Probably the most commercially important recent object-oriented languages are Java, developed by Sun Microsystems, as well as C# and Visual Bas... |
6,708 | Object-oriented programming uses objects, but not all of the associated techniques and structures are supported directly in languages that claim to support OOP. The features listed below are common among languages considered to be strongly class- and object-oriented , with notable exceptions mentioned. Christopher J. D... |
6,709 | Modular programming support provides the ability to group procedures into files and modules for organizational purposes. Modules are namespaced so identifiers in one module will not conflict with a procedure or variable sharing the same name in another file or module. |
6,710 | Objects sometimes correspond to things found in the real world. For example, a graphics program may have objects such as "circle", "square", and "menu". An online shopping system might have objects such as "shopping cart", "customer", and "product". Sometimes objects represent more abstract entities, like an object tha... |
6,711 | Objects can contain other objects in their instance variables; this is known as object composition. For example, an object in the Employee class might contain an object in the Address class, in addition to its own instance variables like "first_name" and "position". Object composition is used to represent "has-a" rela... |
6,712 | The OOP paradigm has been criticized for overemphasizing the use of objects for software design and modeling at the expense of other important aspects . For example, Rob Pike has said that OOP languages frequently shift the focus from data structures and algorithms to types. Steve Yegge noted that, as opposed to functi... |
6,713 | 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 perspectiv... |
6,714 | Rich Hickey, creator of Clojure, described object systems as overly 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. |
6,715 | Alexander Stepanov compares object orientation unfavourably to generic programming: |
6,716 | I find OOP technically unsound. It attempts to decompose the world in terms of interfaces that vary on a single type. To deal with the real problems you need multisorted algebras — families of interfaces that span multiple types. I find OOP philosophically unsound. It claims that everything is an object. Even if it is ... |
6,717 | OOP languages are diverse, but typically OOP languages allow inheritance for code reuse and extensibility in the form of either classes or prototypes. These forms of inheritance are significantly different, but analogous terminology is used to define the concepts of object and instance. |
6,718 | In class-based programming, the most popular style, each object is required to be an instance of a particular class. The class defines the data format or type and available procedures for a given type or class of object. Objects are created by calling a special type of method in the class known as a constructor. Cla... |
6,719 | Depending on the definition of the language, subclasses may or may not be able to override the methods defined by superclasses. Multiple inheritance is allowed in some languages, though this can make resolving overrides complicated. Some languages have special support for other concepts like traits and mixins, though, ... |
6,720 | Abstract classes cannot be instantiated into objects; they exist only for inheritance into other "concrete" classes that can be instantiated. In Java, the final keyword can be used to prevent a class from being subclassed. |
6,721 | In contrast, in prototype-based programming, objects are the primary entities. Generally, the concept of a "class" does not even exist. Rather, the prototype or parent of an object is just another object to which the object is linked. In Self, an object may have multiple or no parents, but in the most popular prototype... |
6,722 | The doctrine of composition over inheritance advocates implementing has-a relationships using composition instead of inheritance. For example, instead of inheriting from class Person, class Employee could give each Employee object an internal Person object, which it then has the opportunity to hide from external code e... |
6,723 | Bob Martin states that because they are software, related classes do not necessarily share the relationships of the things they represent. |
6,724 | It is the responsibility of the object, not any external code, to select the procedural code to execute in response to a method call, typically by looking up the method at run time in a table associated with the object. This feature is known as dynamic dispatch. If the call variability relies on more than the single ty... |
6,725 | Dispatch interacts with inheritance; if a method is not present in a given object or class, the dispatch is delegated to its parent object or class, and so on, going up the chain of inheritance. |
6,726 | Data abstraction is a design pattern in which data are visible only to semantically related functions, to prevent misuse. The success of data abstraction leads to frequent incorporation of data hiding as a design principle in object-oriented and pure functional programming. Similarly, encapsulation prevents external co... |
6,727 | In object oriented programming, objects provide a layer which can be used to separate internal from external code and implement abstraction and encapsulation. External code can only use an object by calling a specific instance method with a certain set of input parameters, reading an instance variable, or writing to an... |
6,728 | If a class does not allow calling code to access internal object data and permits access through methods only, this is also a form of information hiding. Some languages let classes enforce access restrictions explicitly, for example, denoting internal data with the private keyword and designating methods intended for ... |
6,729 | In programming languages, particularly object-oriented ones, the emphasis on abstraction is vital. Object-oriented languages extend the notion of type to incorporate data abstraction, highlighting the significance of restricting access to internal data through methods. Eric S. Raymond has written that object-oriented p... |
6,730 | The "open/closed principle" advocates that classes and functions "should be open for extension, but closed for modification". Luca Cardelli has claimed that OOP languages have "extremely poor modularity properties with respect to class extension and modification", and tend to be extremely complex. The latter point is r... |
6,731 | 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. |
6,732 | Leo Brodie has suggested a connection between the standalone nature of objects and a tendency to duplicate code in violation of the don't repeat yourself principle of software development. |
6,733 | Subtyping – a form of polymorphism – is when calling code can be independent of which class in the supported hierarchy it is operating on – the parent class or one of its descendants. Meanwhile, the same operation name among objects in an inheritance hierarchy may behave differently. |
6,734 | For example, objects of the type Circle and Square are derived from a common class called Shape. The Draw function for each type of Shape implements what is necessary to draw itself while calling code can remain indifferent to the particular type of Shape being drawn. |
6,735 | This is another type of abstraction that simplifies code external to the class hierarchy and enables strong separation of concerns. |
6,736 | A common feature of objects is that methods are attached to them and can access and modify the object's data fields. In this brand of OOP, there is usually a special name such as this or self used to refer to the current object. In languages that support open recursion, object methods can call other methods on the same... |
6,737 | Simula is generally accepted as being the first language with the primary features of an object-oriented language. It was created for making simulation programs, in which what came to be called objects were the most important information representation. Smalltalk is another early example and the one with which much o... |
6,738 | Many widely used languages, such as C++, Java, and Python, provide object-oriented features. Although in the past object-oriented programming was widely accepted, more recently essays criticizing object-oriented programming and recommending the avoidance of these features have been very popular in the developer commun... |
6,739 | Richard Feldman argues that these languages may have improved their modularity by adding OO features, but they became popular for reasons other than being object-oriented. In an article, Lawrence Krubner claimed that compared to other languages OOP languages have no unique strengths, and inflict a heavy burden of unne... |
6,740 | In recent years, object-oriented programming has become especially popular in dynamic programming languages. Python, PowerShell, 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 6. |
6,741 | The Document Object Model of HTML, XHTML, and XML documents on the Internet has 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 t... |
6,742 | The messages that flow between computers to request services in a client-server environment can be designed as the linearizations of objects defined by class objects known to both the client and the server. For example, a simple linearized object would consist of a length field, a code point identifying the class, and ... |
6,743 | Fields defining the data values that form messages, such as their length, code point and data values. |
6,744 | Objects and collections of objects similar to what would be found in a Smalltalk program for messages and parameters. |
6,745 | Managers similar to IBM i Objects, such as a directory to files and files consisting of metadata and records. Managers conceptually provide memory and processing resources for their contained objects. |
6,746 | A client or server consisting of all the managers necessary to implement a full processing environment, supporting such aspects as directory services, security, and concurrency control. |
6,747 | The initial version of DDM defined distributed file services. It was later extended to be the foundation of Distributed Relational Database Architecture . |
6,748 | Challenges of object-oriented design are addressed by several approaches. The most common is known as the design patterns codified by Gamma et al.. More broadly, the term "design patterns" can be used to refer to any general, repeatable, solution pattern to a commonly occurring problem in software design. Some of these... |
6,749 | 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 m... |
6,750 | Design Patterns: Elements of Reusable Object-Oriented Software is an influential book published in 1994 by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, often referred to humorously as the "Gang of Four". Along with exploring the capabilities and pitfalls of object-oriented programming, it describes 23 ... |
6,751 | The book describes the following patterns: |
6,752 | Both object-oriented programming and relational database management systems are extremely common in software today. Since relational databases do not store objects directly , there is a general need to bridge the two worlds. The problem of bridging object-oriented programming accesses and data patterns with relational... |
6,753 | There are also object databases that can be used to replace RDBMSs, but these have not been as technically and commercially successful as RDBMSs. |
6,754 | 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 or that real-world mapping is even a worthy goal; Bertrand Meyer argues in Object-Oriented Software Construction that a program is not a model of the worl... |
6,755 | However, Niklaus Wirth 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 behaviors" . |
6,756 | Steve Yegge and others noted that natural languages lack the OOP approach of strictly prioritizing things before actions . This problem may cause OOP to suffer more convoluted solutions than procedural programming. |
6,757 | OOP was developed to increase the reusability 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, developing transparent control flow becomes more import... |
6,758 | Responsibility-driven design 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... |
6,759 | SOLID is a mnemonic invented by Michael Feathers which spells out five software engineering design principles: |
6,760 | GRASP is another set of guidelines advocated by Craig Larman. |
6,761 | 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. |
6,762 | 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: |
6,763 | Attempts to find a consensus definition or theory behind objects have not proven very successful , 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 ... |
6,764 | The term is often used in contrast to declarative programming, which focuses on what the program should accomplish without specifying all the details of how the program should achieve the result. |
6,765 | Procedural programming is a type of imperative programming in which the program is built from one or more procedures . The terms are often used as synonyms, but the use of procedures has a dramatic effect on how imperative programs appear and how they are constructed. Heavy procedural programming, in which state change... |
6,766 | Procedural programming could be considered a step toward declarative programming. A programmer can often tell, simply by looking at the names, arguments, and return types of procedures , what a particular procedure is supposed to do, without necessarily looking at the details of how it achieves its result. At the same ... |
6,767 | The programming paradigm used to build programs for almost all computers typically follows an imperative model. Digital computer hardware is designed to execute machine code, which is native to the computer and is usually written in the imperative style, although low-level compilers and interpreters using other paradig... |
6,768 | From this low-level perspective, the program state is defined by the contents of memory, and the statements are instructions in the native machine language of the computer. Higher-level imperative languages use variables and more complex statements, but still follow the same paradigm. Recipes and process checklists, wh... |
6,769 | Assignment statements, in imperative paradigm, perform an operation on information located in memory and store the results in memory for later use. High-level imperative languages, in addition, permit the evaluation of complex expressions, which may consist of a combination of arithmetic operations and function evaluat... |
6,770 | Early in the development of high-level programming languages, the introduction of the block enabled the construction of programs in which a group of statements and declarations could be treated as if they were one statement. This, alongside the introduction of subroutines, enabled complex structures to be expressed by ... |
6,771 | Many imperative programming languages are abstractions of assembly language. |
6,772 | The earliest imperative languages were the machine languages of the original computers. In these languages, instructions were very simple, which made hardware implementation easier but hindered the creation of complex programs. FORTRAN, developed by John Backus at International Business Machines starting in 1954, was ... |
6,773 | The 1980s saw a rapid growth in interest in object-oriented programming. These languages were imperative in style, but added features to support objects. The last two decades of the 20th century saw the development of many such languages. Smalltalk-80, originally conceived by Alan Kay in 1969, was released in 1980, by ... |
6,774 | FORTRAN was unveiled as "The IBM Mathematical FORmula TRANslating system." It was designed for scientific calculations, without string handling facilities. Along with declarations, expressions, and statements, it supported: |
6,775 | It succeeded because: |
6,776 | However, non IBM vendors also wrote Fortran compilers, but with a syntax that would likely fail IBM's compiler. The American National Standards Institute developed the first Fortran standard in 1966. In 1978, Fortran 77 became the standard until 1991. Fortran 90 supports: |
6,777 | COBOL stands for "COmmon Business Oriented Language." Fortran manipulated symbols. It was soon realized that symbols did not need to be numbers, so strings were introduced. The US Department of Defense influenced COBOL's development, with Grace Hopper being a major contributor. The statements were English-like and ver... |
6,778 | COBOL's development was tightly controlled, so dialects did not emerge to require ANSI standards. As a consequence, it was not changed for 15 years until 1974. The 1990s version did make consequential changes, like object-oriented programming. |
6,779 | ALGOL stands for "ALGOrithmic Language." It had a profound influence on programming language design. Emerging from a committee of European and American programming language experts, it used standard mathematical notation and had a readable structured design. Algol was first to define its syntax using the Backus–Naur f... |
6,780 | block structure, where variables were local to their block |
6,781 | arrays with variable bounds |
6,782 | "for" loops |
6,783 | functions |
6,784 | recursion |
6,785 | Algol's direct descendants include Pascal, Modula-2, Ada, Delphi and Oberon on one branch. On another branch there's C, C++ and Java. |
6,786 | BASIC stands for "Beginner's All Purpose Symbolic Instruction Code." It was developed at Dartmouth College for all of their students to learn. If a student did not go on to a more powerful language, the student would still remember Basic. A Basic interpreter was installed in the microcomputers manufactured in the late... |
6,787 | Basic pioneered the interactive session. It offered operating system commands within its environment: |
6,788 | However, the Basic syntax was too simple for large programs. Recent dialects added structure and object-oriented extensions. Microsoft's Visual Basic is still widely used and produces a graphical user interface. |
6,789 | C programming language got its name because the language BCPL was replaced with B, and AT&T Bell Labs called the next version "C." Its purpose was to write the UNIX operating system. C is a relatively small language -- making it easy to write compilers. Its growth mirrored the hardware growth in the 1980s. Its growth ... |
6,790 | C allows the programmer to control in which region of memory data is to be stored. Global variables and static variables require the fewest clock cycles to store. The stack is automatically used for the standard variable declarations. Heap memory is returned to a pointer variable from the malloc function. |
6,791 | In the 1970s, software engineers needed language support to break large projects down into modules. One obvious feature was to decompose large projects physically into separate files. A less obvious feature was to decompose large projects logically into abstract datatypes. At the time, languages supported concrete dat... |
6,792 | In object-oriented jargon, abstract datatypes are called classes. However, a class is only a definition; no memory is allocated. When memory is allocated to a class, it's called an object. |
6,793 | Object-oriented imperative languages developed by combining the need for classes and the need for safe functional programming. A function, in an object-oriented language, is assigned to a class. An assigned function is then referred to as a method, member function, or operation. Object-oriented programming is executing... |
6,794 | Object-oriented languages support a syntax to model subset/superset relationships. In set theory, an element of a subset inherits all the attributes contained in the superset. For example, a student is a person. Therefore, the set of students is a subset of the set of persons. As a result, students inherit all the attr... |
6,795 | C++ was originally called "C with Classes." It was designed to expand C's capabilities by adding the object-oriented facilities of the language Simula. |
6,796 | An object-oriented module is composed of two files. The definitions file is called the header file. Here is a C++ header file for the GRADE class in a simple school application: |
6,797 | A constructor operation is a function with the same name as the class name. It is executed when the calling operation executes the new statement. |
6,798 | A module's other file is the source file. Here is a C++ source file for the GRADE class in a simple school application: |
6,799 | Here is a C++ header file for the PERSON class in a simple school application: |
6,800 | Here is a C++ source file for the PERSON class in a simple school application: |
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