Editing Legacy system (section)

==Additional uses of the term ''Legacy'' in computing==
The term ''legacy support'' is often used in conjunction with legacy systems. The term may refer to a feature of modern software.  For example, [[Operating system]]s with "legacy support" can detect and use older hardware. The term may also be used to refer to a business function; e.g. a software or hardware vendor that is supporting, or providing [[software maintenance]], for older products.

A "legacy" product may be a product that is no longer sold, has lost substantial market share, or is a version of a product that is not current.  A legacy product may have some advantage over a modern product making it appealing for customers to keep it around. A product is only truly "obsolete" if it has [[pareto efficiency|an advantage to nobody]]—if no person making a rational decision would choose to acquire it new.

The term "legacy mode" often refers specifically to [[backward compatibility]]. A software product that is capable of performing as though it were a previous version of itself, is said to be "running in legacy mode".  This kind of feature is common in operating systems and web browsers, where many applications depend on these underlying components.

The [[Mainframe computer|computer mainframe]] era saw many applications running in legacy mode. In the modern business computing environment, [[n-tier]], or [[3-tier]] [[Computer architecture|architectures]] are more difficult to place into legacy mode as they include many components making up a single system.

[[Virtual machine|Virtualization]] technology is a recent innovation allowing legacy systems to continue to operate on modern hardware by running older operating systems and browsers on a software system that emulates legacy hardware.