"The book is great! It's clear and easy to read, with loads of examples that showed my students what to do."        -- Larry Snyder, Emeritus Professor, University of Washington, Department of Computer Science and Engineering “Having the TouchDevelop book available made our events so much easier. Students could figure things out for themselves with help from the book.” -- Jennifer Marsman, Microsoft Principal Developer Evangelist Mobiledevices such as smartphones and tablets are set to become the main computersthat virtually all people will own and carry with them at all times. And yet,mobile devices are not yet used for all computing tasks. A project at MicrosoftResearch was created to answer a simple question: “It is possible to createinteresting apps directly on a smartphone or tablet, without using a separatePC or a keyboard?” The result is TouchDevelop, a programming environment thatruns on all modern mobile devices such as Windows Phone, iPhone, iPad, Androidphones and tablets, and also on PCs and Macs. This book walks you through all of the screens of the TouchDevelop app, and itpoints out similarities and differences of the TouchDevelop language comparedto other programming languages. For users, the book can serve as a handyreference next to the phone. The book systematically addresses all programminglanguage constructs, starting from the very basic constructs such as variablesand loops. The book also explores many of the phone sensors and data sourceswhich make creating apps for mobile devices so rewarding. If you are new to programming with TouchDevelop, or if you have not yet workedon touchscreen devices, we suggest that you read the book starting from Chapter1. If you are already familiar with the basic paradigm of the TouchDevelopprogramming environment, then feel free to jump ahead to the later chaptersthat address particular topic areas. This book is written from theperspective of a person developing their code using a web browser. TheTouchDevelop Web App runs in many modern browsers on many different devicesincluding smartphones and tablets, Macs, PC. All screenshots and navigationinstructions refer to the TouchDevelop Web App running in a browser. ForWindows Phone, there is a dedicated TouchDevelop app in the Windows Phone Storewhich gives access to many more sensors and data sources. Starting with theTouchDevelop app v3.0 for Windows Phone 8, the phone app will share the samelook and navigation structure and all features of the Web App.