Legacy System

Definition - What does Legacy System mean?

A legacy system, in the context of computing, refers to outdated computer systems, programming languages or application software that are used instead of available upgraded versions.

Legacy systems also may be associated with terminology or processes that are no longer applicable to current contexts or content, thus creating confusion.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.

Techopedia explains Legacy System

A legacy system is not necessarily defined by age. Legacy may refer to lack of vendor support or a system's incapacity to meet organizational requirements. For example, a large mainframe may use a 64-bit Java, while a Linux platform might utilize code from the 1960s. Legacy conditions refer to a system's difficulty (or inability) to be maintained, supported or improved. A legacy system is usually incompatible with newly purchased systems.

Legacy systems are high maintenance and may involve intricate patching and modifications. Porting techniques are often used for software adjustments or adaptation. Older hardware may require added compatibility layers to facilitate device functionality in incompatible environments.

An organization might continue to use legacy systems for a wide range of reasons, such as the following:

  • "If it ain't broke, don't fix it!" The system might work adequately.
  • The system is complex, and documentation is poor. Simply defining scope can be difficult.
  • A redesign is costly, due to complexity or monolithic architecture.
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