William N. Joy (born 1954), commonly known as Bill Joy, co-founded Sun Microsystems in 1982 along with Vinod Khosla, Scott McNealy and Andy Bechtolsheim, and served as chief scientist at the company until 2003.

Joy received his B.S. in Electrical Engineering from the University of Michigan and his M.S. in Electrical Engineering and Computer Science from UC Berkeley.

Bill Joy was the person largely responsible for the authorship of Berkeley UNIX, also known as BSD, from which springs many modern forms of UNIX, including FreeBSD, NetBSD, and OpenBSD. Two of his most notable contributions were the vi editor and the csh shell. Joy was also a primary figure in the development of the Java programming language, and JINI.

In 2000 he gained notoriety with the publication of his article in Wired Magazine, "Why the future doesn't need us", in which he put forward what some have described as a "neo-Luddite" position that he was convinced by the growing advances in genetic engineering and nanotechnology that intelligent robots would replace humanity, at the very least in intellectual and societal dominance, in the relatively near future.

On September 9, 2003 Sun said that Bill Joy was leaving the company and that he "is taking time to consider his next move and has no definite plans.".

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