C4 was a Macintosh software developers conference held in Chicago, Illinois. The conference ran from 2006[1] through 2009. It was created by Jonathan Rentzsch after the demise of MacHack.[2] In May 2010 Rentzsch announced[3] that he would no longer operate the conference due to a dissatisfaction with Apple's policies toward iPhone OS development and the lack of a strong negative reaction from the Apple developer community.[4]