Apple's C++ development tool that shipped with OS X public beta's development CD, a low-end competitor to Metrowerks Codewarrior. Mainly, it is a front-end to the gcc compiler, with support for many Apple-specific technologies such as bundles and KEXT's. It also supports Objective C.
It also integrates another tool, Interface Builder, which allows you to create NIB's, which are Carbon Dialog box resources.