Software Maintenance Cost Estimation in Legacy Applications

Abstract

Software maintenance cost estimation is important in legacy applications because older systems often require continuous correction, adaptation, enhancement, and support while operating with outdated architectures, limited documentation, and fragile dependencies. Legacy applications may contain obsolete programming languages, complex business rules, duplicated code, hard-coded configurations, weak test coverage, and integration constraints that increase maintenance effort over time. Traditional cost estimation methods may underestimate maintenance work because they often focus on visible change requests and ignore hidden factors such as code complexity, technical debt, defect recurrence, developer knowledge gaps, and environment compatibility issues. This article focuses on software maintenance cost estimation in legacy applications by examining maintenance history, defect frequency, module complexity, change effort, documentation quality, dependency risk, and resource availability. The study discusses how these indicators can be used to estimate effort, prioritize high-cost modules, and support better maintenance planning. The article concludes that structured maintenance cost estimation can improve budgeting accuracy, reduce unexpected support costs, guide modernization decisions, and strengthen long-term management of legacy software systems.