What is Legacy Software and How Does it Define the Technology Landscape?

Legacy Software is a crucial aspect of the IT industry that affects the daily operations of many organizations. Although modern software applications are becoming increasingly sophisticated, a substantial portion of businesses still rely on older systems. According to Robert L. Glass, roughly 80% of software maintenance costs are directed towards legacy systems. This statistic illustrates the importance of understanding the nature of legacy software – and how it impacts various industries. In this article, we will discuss the definition, benefits, use cases, and best practices for using legacy software.

“Software is like entropy: It is difficult to grasp, weighs nothing, and obeys the Second Law of Thermodynamics; i.e., it always increases.” – Norman Ralph Augustine

What is Legacy Software? Definition of Legacy Application

Legacy Software refers to computer programs, applications or systems that have been in use for an extended period, despite being outdated or overtaken by newer technologies. This term is often associated with older software that was designed, created, or written using older programming languages or platforms. Legacy software may continue to be utilized because updating or replacing the system can be expensive, time-consuming, or pose significant risks.

ℹ️ Synonyms: Outdated software, Antique software, Old software, Obsolete software, Ancient software

How it Works

Legacy software works similarly to other software applications; it sits on top of the operating system (OS) and often communicates and integrates with other systems or software. One primary characteristic is the hardware and software environment it exists in, which is often outdated or unsupported by current standards. This makes maintaining, supporting, and integrating challenging and sometimes inefficient, as modern technologies may not easily interact with these older systems. However, these systems continue to be used by businesses because they have proven to be reliable and stable over time.

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Benefits of using Legacy Software

While legacy software may seem outdated, there are several advantages to using these older systems. Some benefits include:

  • Reliability and Stability: Legacy systems have been used for many years, and because of this, they tend to be more reliable and stable than newer software systems.
  • Low Acquisition Costs: Because legacy software is older, it is often cheaper to acquire, making it beneficial for businesses on a tight budget.
  • Compatibility and Integration: Many businesses have tailored their operations around legacy software, making it challenging to move away from these systems. Additionally, some older applications can seamlessly interact with newer software, offering compatibility benefits.
  • Domain Expertise and Knowledge: Over time, employees and stakeholders become well-versed in the intricacies of legacy software, adding value to organizations by leveraging domain knowledge and expertise.

Legacy Software Use Cases

Many organizations across various industries continue to rely on legacy software. Some examples of use cases include:

– Banking and finance institutions still utilizing mainframe systems for processing critical transactions.
– Manufacturing companies utilizing older computer numerical control (CNC) systems for machine operations.
– Healthcare providers relying on older electronic health record (EHR) systems to manage patient data.
– Retail establishments using point-of-sale (POS) software that was developed and deployed years ago.

These examples demonstrate that legacy software remains an integral part of daily business operations for many organizations.

Best Practices

To ensure the continued success of businesses relying on legacy software, implementing best practices is essential. Key considerations involve balancing the need for integration, security, and support with the goal of preserving the stability and functionality of these systems. Businesses should focus on maintaining stringent security protocols, investing in robust support infrastructure, and regularly reviewing and updating their software to keep it aligned with current needs. Moreover, organizations should have a long-term strategy for the transition, modernization, or replacement of legacy software when necessary.

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Most Recommended Books about Legacy Software

If you’re interested in further exploring the topic of legacy software, we recommend the following books:

1. Working Effectively with Legacy Code by Michael Feathers – This book provides practical techniques for refactoring, testing, and maintaining older software systems.
2. Refactoring to Patterns by Joshua Kerievsky – A guide to incorporating powerful patterns and refactoring techniques in legacy software projects.
3. Modernizing Legacy Systems: Software Technologies, Engineering Processes, and Business Practices by Robert C. Seacord – This book discusses methods to incrementally modernize legacy systems while preserving business operations.


Legacy software is an essential component of the IT landscape, with many organizations still dependent on these older systems. Understanding what constitutes a legacy system, its benefits, use cases, and best practices will enable businesses to make informed decisions about the management and potential modernization of these software applications. By leveraging domain knowledge, ensuring security, stability, and compatibility, organizations can continue to maintain and capitalize on their investment in legacy software systems.

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Back in 2013, I founded Echo with the simple business idea: "Connect great tech companies around the globe with the brightest software engineers in Eastern Europe." We've employed hundreds of talents so far and keep going.
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li-url Lou Reverchuk

IT Entrepreneur

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