500 Lines or Less

500 Lines or Less is the source repository for the fourth book in the Architecture of Open Source Applications series. The project focuses on small but meaningful programs that solve classic software engineering problems in no more than 500 lines of source code. Its goal is to make software design lessons easier to study by using compact, readable examples instead of large production systems. Each chapter walks through design decisions, tradeoffs, module boundaries, interfaces, and extension points. The book is especially useful for developers who want to understand how experienced programmers think while building real systems. It works as both an educational text and a practical reference for studying architecture through code.