Mac OS X Developer Preview 1

Mac OS X Developer Preview 1 is the first Developer Preview of Mac OS X Public Beta. This build still included the Platinum theme, which would be replaced with the Aqua theme later in Developer Preview 3. Unlike the later Developer Previews, it is still similar to Mac OS X Server 1.x and the installation media boots to a Mac OS 8.6 pre-installation environment instead of instantly booting to setup. It was introduced at the Worldwide Developers Conference in 1999, showcasing the Darwin kernel to Mac OS and the bases for the completed operating system.