Learning to create IPhone and IPad web and other applications is an extremely fast growing field and this primer will provide some details on getting started. Naturally, the main difference between IPhone and IPad apps is that IPad applications must use a larger screen resolution. iPhone OS apps are mostly officially licensed and sold from the Apple Store although hacks are available to install unauthorized applications.
Figure: iPhone OS technology layers
IPhone, IPod Touch and Ipad applications run on the IPhone OS and can be developed using IPhone SDK and Objective-C, C/C++ can also be used – the SDK contains Xcode templates to help beginners get started. Most User apps use the Foundation and UIKit frameworks at the top level Cocoa touch layer of the IPhone OS (above). Other tecnology layers in the IPhone OS include the Media and lower level Core OS and Core services and require some more advanced programming.
Tips for Getting Started
Visit the IPhone OS Developer site
View the related iPhone iPad Programming guides
Download the IPhone SDK
Prepare your Objective-C or C/C++ programming environment.
Make some simple apps with the Xcode templates.
Move on the advanced tutorials.