Aaron Hillegass (born 1969) Is the founder and CLO (Chief Learning Officer) of Big Nerd Ranch. Aaron is best known to many programmers as the author of Objective-C: The Big Nerd Ranch Guide, Cocoa Programming for Mac OS X, and iOS Programming: The Big Nerd Ranch Guide.
Between 1995 - 1997 he was employed at NeXT as a developer and trainer. In 1997, NeXT merged with Apple Computer. Hillegass elected to leave his role to start his own dot-com business. In 2000, he was then contracted by Apple to help train their software developers in the Cocoaapplication programming interface (API), an evolution of the NEXTSTEP API. This led to the creation of Big Nerd Ranch, a professional services company that originally worked only with Apple technologies.