Bertrand Serlet, one of the finest software developer of Apple Inc would leave the company after more than a decade spent developing Apple's signature operating system. Craig Federighi, currently the vice president of Mac Software Engineering, will assume Serlet's responsibilities and report to chief executive Steve Jobs, Apple said in a statement. Federighi worked a previous stint at Apple and returned again to the company in 2009. The departing Serlet, who joined the company in 1997, concentrated on developing and releasing the Mac OS X operating system. Serlet, whose title was senior vice president of Mac Software Engineering, said in a statement that he wanted to focus on science rather than products.