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 do not 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— even if 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 When the manufacturer upgrades a platform (or the platform is superseded), the code may no longer work without changes, and becomes legacy code.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 also apply to executable code that no longer runs on a later 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.
Read more about Legacy Code: Modern Interpretations
Famous quotes containing the words legacy and/or code:
“What is popularly called fame is nothing but an empty name and a legacy from paganism.”
—Desiderius Erasmus (c. 1466–1536)
“Wise Draco comes, deep in the midnight roll
Of black artillery; he comes, though late;
In code corroborating Calvin’s creed
And cynic tyrannies of honest kings;
He comes, nor parlies; and the Town, redeemed,
Gives thanks devout; nor, being thankful, heeds
The grimy slur on the Republic’s faith implied,
Which holds that Man is naturally good,
And—more—is Nature’s Roman, never to be
scourged.”
—Herman Melville (1819–1891)