TempleOS (formerly J Operating System, SparrowOS and LoseThos) is a biblical-themed lightweight operating system created by the American programmer Terry A. Davis. He developed the system alone over the course of 10 years. It was designed to be the Third Temple, according to Davis, and uses an interface similar to a mixture of DOS and Turbo C. Davis describes the operating system as a modern x86-64 Commodore 64 with a variation of C (named HolyC) in place of BASIC.