A software component is a modular unit of

software Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications. The history of software is closely tied to the development of digital comput ...

that encapsulates specific functionality. The desired characteristics of a component are reusability and maintainability.

Value

Components allow

software development Software development is the process of designing and Implementation, implementing a software solution to Computer user satisfaction, satisfy a User (computing), user. The process is more encompassing than Computer programming, programming, wri ...

to assemble software with reliable parts rather than writing

code In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communicati ...

for every aspect; allowing for

implementation Implementation is the realization of an application, execution of a plan, idea, scientific modelling, model, design, specification, Standardization, standard, algorithm, policy, or the Management, administration or management of a process or Goal ...

to be more like factory assembly than custom building.

Attributes

Desirable attributes of a component include but are not limited to: * Cohesive encapsulates related functionality * Reusable * Robust * ''Substitutable'' can be replaced by another component with the same interface * Documented * Tested

Third-party

Some components are built in-house by the same organization or team building the software system. Some are third-party, developed elsewhere and assembled into the software system.

Component-based software engineering

For large-scale systems,

component-based development Component-based software engineering (CBSE), also called component-based development (CBD), is a style of software engineering that aims to construct a software system from software component, components that are loosely-Coupling (computer program ...

encourages a disciplined process to manage

complexity Complexity characterizes the behavior of a system or model whose components interact in multiple ways and follow local rules, leading to non-linearity, randomness, collective dynamics, hierarchy, and emergence. The term is generally used to c ...

Framework

Some components conform to a framework technology that allows them to be consumed in a well-known way. Examples include: CORBA, COM, Enterprise JavaBeans, and the .NET Framework.

Modeling

Component-based-Software-Engineering-example2

Component design is often modeled visually. In Unified Modeling Language (UML) 2.0 a component is shown as a rectangle, and an interface is shown as a lollipop to indicate a provided interface and as a socket to indicate consumption of an interface.

History

The idea of reusable software components was promoted by Douglas McIlroy in his presentation at the NATO Software Engineering Conference of 1968. (One goal of that conference was to resolve the so-called software crisis of the time.) In the 1970s, McIlroy put this idea into practice with the addition of the

pipeline A pipeline is a system of Pipe (fluid conveyance), pipes for long-distance transportation of a liquid or gas, typically to a market area for consumption. The latest data from 2014 gives a total of slightly less than of pipeline in 120 countries ...

feature to the

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

Brad Cox Brad J. Cox (May 2, 1944 – January 2, 2021) was an American computer scientist who was known mostly for creating the Objective-C programming language with his business partner Tom Love and for his work in software engineering (specifically so ...

refined the concept of a software component in the 1980s. He attempted to create an infrastructure and market for reusable third-party components by inventing the

Objective-C Objective-C is a high-level general-purpose, object-oriented programming language that adds Smalltalk-style message passing (messaging) to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was ...

programming language.

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

introduced System Object Model (SOM) in the early 1990s.

Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...

introduced Component Object Model (COM) in the early 1990s. Microsoft built many domain-specific component technologies on COM, including Distributed Component Object Model (DCOM), Object Linking and Embedding (OLE), and ActiveX.

References

{{Reflist Software architecture Software development Software engineering