aosabook/500lines

500 Lines or Less is the source repository for a programming book of the same name, the fourth volume in the Architecture of Open Source Applications series. The book takes a different approach from most programming tutorials: instead of teaching syntax or introducing frameworks, it explains how experienced programmers think about design decisions, why they split code into particular modules, when to use inheritance versus composition (two ways of organizing code), and how to anticipate future changes. Each chapter is a walkthrough of a small, self-contained program, no more than 500 lines of code, that solves a classic software engineering problem. Examples include a web crawler, a spreadsheet, a static analysis tool, an object model, and a pedometer. Each program was written by a different experienced contributor who explains the thinking behind the design choices made along the way. The book is part of a series aimed at helping programmers understand how well-known types of software are actually built. All written content is under a Creative Commons license (free to share with attribution for non-commercial use), and all code is under the MIT license. Someone would read this to develop better intuitions about software architecture and design at a scale they can fully grasp and study.