The iPad SDK is more than just an extension of the iPhone and iPod Touch SDK, so don't expect to write once and test everywhere Last weekend’s edition of the New York Times included, as expected, several iPad-related articles. The one that especially caught my eye was about the developers of DoodleJump, a popular iPhone game, rushing home from the Apple Store Saturday to test the iPad version of their game, developed using a simulator, on real hardware. It didn’t surprise me to learn that they had to spend hours adjusting the game for playability on the new device and felt vindicated in their decision not to release the iPad version until they had shaken down the game on actual hardware.This week brought the “beta” book “iPad Programming: A Quick-Start Guide for iPhone Developers,” by Daniel H. Steinberg and Eric T. Freeman (Pragmatic Bookshelf, $34.95). As the title implies, this book assumes that you already know how to build iPhone applications with the SDK and need to learn what’s different about iPad programming.[ InfoWorld’s Peter Wayner takes you through the good and the bad of developing iPad apps in his “Inside the iPad SDK: Bigger screens, continued frustrations.” ] Right off the bat, Steinberg and Freeman say, “We don’t merely want you to write apps that run on an iPad, we want you to write apps that are perfect for the platform.” While they go on to show you how to use the iPhone compatibility mode and how to build “universal” iPhone/iPad applications, their comment on their own universal app is, “Wow. That looks terrible. Look at all that wasted space.” Then they show you how to build a separate binary for the iPad so that the appearance can be tweaked.This beta book is roughly one-third done. What’s available are two general chapters on making the iPhone-to-iPad transition, and a chapter each on iPad gestures (a significantly enhanced API) and playing movies (a new API). Still to come are chapters on the new drawing APIs, Core Text, document sharing, and interdevice connections.To get started as an iPhone or iPad developer, you need to register at Apple for $99 per year. You’ll need to have Mac OS X 10.6.2 running on an Intel-based Mac, and you’ll need to download the latest tools and SDKs from Apple. Knowing Cocoa and Objective-C is a starting point. Good luck! This article, “For developers, iPhone-to-iPad is a bigger jump than you’d expect,” was originally published at InfoWorld.com. Read more of Martin Heller’s Strategic Developer blog and follow the latest news on software development and mobile computing at InfoWorld.com. Development ToolsTechnology Industry