Legacy Systems

A legacy system, in the context of computing, refers to outdated computer systems, programming languages or application software that are used instead of available upgraded versions. Legacy systems also may be associated with terminology or processes that are no longer applicable to current contexts or content, thus creating confusion. In theory, it would be great to be able to have immediate access to use the most advanced technology. But in reality, most organizations have legacy systems - to some extent. A legacy system may be problematic, due to compatibility issues, obsoletion or lack of security support. A legacy system is also known as a legacy platform.

Gartner defines legacy system as, "An information system that may be based on outdated technologies, but is critical to day-to-day operations. Replacing legacy applications and systems with systems based on new and different technologies is one of the information systems (IS) professional’s most significant challenges. As enterprises upgrade or change their technologies, they must ensure compatibility with old systems and data formats that are still in use."