Apple has been talking up its iPhone software development kit at the Worldwide Developers Conference in San Francisco.

Plans for the SDK were announced in October after Apple was criticised for its decision to limit developers to browser-based applications. The kit has been in beta for several months.

Apple promised that the SDK will give developers the same access to the iPhone's hardware enjoyed by the firm's in-house programmers.

The tool will also be familiar to Mac OS developers, according to Scott Forstall, senior vice president of iPhone software.

Forstall paraded a number of companies, including Sega, eBay and Typepad, which showcased early versions of their own iPhone applications.

Developers will be able to create software in Apple's existing X-Code development environment, and much of the iPhone's code, from its APIs down to its kernel, is very similar to Mac OS.

The company even offers Cocoa Touch, a touchpad development tool based on the OS X Cocoa framework.

Developers will be able to test code on any computer by way of the iPhone Simulator, a PC-based tool that recreates the iPhone environment.

Apple then plans to allow developers a number of ways to distribute iPhone applications.

Commercial applications will be sold through the AppStore on iTunes. Developers will be able to set their own prices for the software and Apple will pocket 30 per cent of the sales.

For in-house developers, the company will offer a feature to distribute software within a company.

An enterprise will be able to authorise a set of iPhones for use with its specific network. In-house applications can then be downloaded to workstations on that network and synchronised to the iPhones.

Apple also plans to issue a service for students and instructors known as Ad-Hoc. This will allow a teacher to authorise up to 100 iPhones to share and repost code within a closed network.

Students and instructors will then be able to review and exchange applications for the device.

Apple plans to release the final version of the iPhone SDK by September.