This MedLibrary.org supplementary page on Legacy code is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
 |
This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. (February 2008) |
Legacy code is source code that relates to a no-longer supported or manufactured operating system or other computer technology. The term can also mean code inserted into modern software for the purpose of maintaining an older or previously supported feature — for example supporting a serial interface even though many modern systems don't have a serial port. It may also be in the form of supporting older file formats that may have been encoding in non-ASCII characters, such as EBCDIC.
In practice, most source code has some dependency on the platform for which it is designed—unless a programmer uses a platform-independent programming language like Java, it is hard to write a large, useful program that is totally independent of its environment. When the manufacturer upgrades or supersedes the platform, the code will no longer work without changes, and becomes legacy code. A large part of the task of a software engineer is to continually alter code to prevent this.
While the term usually refers to source code, it can occasionally be heard applied to executable code that no longer runs on a modern version of a system, or requires a compatibility layer to do so. An example would be a classic Macintosh application which will not run natively on Mac OS X, but runs inside the Classic environment, or a Win16 application running on Windows XP using the Windows on Windows feature in XP.
Modern interpretations
More recently, the software engineering community has developed other interpretations for the term legacy code. Among the most prevalent are source code inherited from someone else and source code inherited from an older version of the software. Michael Feathers' Working Effectively with Legacy Code (ISBN 0-13-117705-2) introduced a definition of legacy code as code without tests, which reflects the perspective of legacy code being difficult to work with in part due to a lack of automated regression tests. He also defined Characterization Tests to start putting legacy code under test.
See also
Wikipedia content modification information:
- This page was last modified on 26 May 2008, at 11:02.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Legacy code".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.