If you read in Wikipedia on Mobile Development, you will find a concise description of the "official" way to develop iPhone applications:
The iPhone and iPod Touch SDK uses Objective C, based on the C programming language. Currently, is only available on Mac OS X 10.5 and is the only way to write an iPhone application. All applications must be cleared by Apple before being hosted on the AppStore, the sole distribution channel for iPhone and iPod touch applications.
With Tersus as an iPhone development tool, things are much simpler. You get rapid iPhone development and seamless deployment:
Quick Tutorial #1 - Sales Dashboard
Quick Tutorial #2 - Displaying data from Twitter
Quick Tutorial #3 - Developing an iPhone Shopping List application
Quick Tutorial #4 - Creating a native iPhone application using the iPhone camera [Hebrew Version]
Also available at http://www.youtube.com/watch?v=JC34-nIWMUc
Documentation - The iPhone Palette
Native iPhone Applications vs. iPhone Web Applications
Enterprise Deployment
Security
Deployment as a native iPhone application
Hybrid Web Applications (Desktop + iPhone)
iPhone Development on Mac
iPhone Development on Windows
iPhone Development on Linux
Cross-Device Development
Offline Applications and Client-Side Database
Style Control through CSS
Right to Left Languages
Use Cases: Well Field Data Collection
More Examples: Memory Game
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