Code reuse

From Wikipedia, the free encyclopedia

Code reuse, also called software reuse, is the use of existing software, or software knowledge, to build new software. Ad hoc reuse has been practiced from the earliest days of programming. Programmers have always reused sections of code, templates, functions, and procedures. Software reuse as a recognized area of study in software engineering, however, dates only from 1968 when Douglas McIlroy of Bell Laboratories proposed basing the software industry on reusable components.

Reusable software, or software knowledge items, are called reusable assets. Assets may be designs, requirements, test cases, architectures, etc.

Perhaps the most well known reusable asset is code. Code reuse is the idea that a partial or complete computer program written at one time can be, should be, or is being used in another program written at a later time. The reuse of programming code is a common technique which attempts to save time and energy by reducing redundant work.

A very common example of code reuse is the technique of using a software library. Many common operations, such as converting information among different well-known formats, accessing external storage, interfacing with external programs, or manipulating information (numbers, words, names, locations, dates, etc.) in common ways, are needed by many different programs. Authors of new programs can use the code in a software library to perform these tasks, instead of "re-inventing the wheel", by writing fully new code directly in a program to perform an operation. Library implementations often have the benefit of being well-tested, and covering unusual or arcane cases. Disadvantages include the inability to tweak details which may affect performance or the desired output, and the time and cost of acquiring, learning, and configuring the library.

The software library is a good example of abstraction. Programmers may decide to create internal abstractions so that certain parts of their program can be re-used, or may create custom libraries for their own use.

For newly written code to use a piece of existing code, some kind of interface, or means of communication, must be defined. These commonly include a "call" or use of a subroutine, object, class, or prototype. In organizations, such practices are formalized and standardized by software product line engineering.

The general practice of using a prior version of an extant program as a starting point for the next version, is also a form of code reuse.

Some code reuse involves simply copying some or all of the code from an existing program into a new one.

Many researchers have worked to make reuse faster, easier, more systematic, and an integral part of the normal process of programming. These are some of the main goals behind the invention of object-oriented programming, which became one of the most common forms of formalized reuse. A somewhat later invention is generic programming.

Another, newer means is to use software "generators", programs which can create new programs of a certain type, based on a set of parameters that users choose. Fields of study about such systems are generative programming and metaprogramming.

[edit] See also

• Implementation inheritance
• Inheritance semantics
• Procedural programming
• Virtual inheritance

[edit] External links

• Software Reuse - information and events concerning the practice of software reuse.
• RiSE - Reuse in Software Engineering
• http://frakes.cs.vt.edu/renews.html