UNIX originated in 1969 when Ken Thompson, facinated with the game Space Travel, decided it would be easier to write an operating system for the DEC PDP-7 to run his game rather than to write a PDP-7 cross compiler on the lab's GE-645. UNIX inhereted features from MULTiplexed Information and Computer System (MULTICS), a project that Bell Labs, General Electric and RAND were involved in. However, Ken never bothered to include more important features of MULTICS. After all, UNIX was just for a game. But, UNIX became popular in the labs and soon was given away to Universites. The system was never standardized though its name suggested UNIformity. The west coast was given the UNIX source code and soon Berkeley UNIX (BSD) was born.

SYSTEM 5 and BSD have a distinct flavor which sets them apart. Many view SYSTEM 5 hackers as being conservative while BSD hackers are seen as being liberal.