Columbus UNIX (or CB UNIX) was, according to Marc Rochkind, a variant of the UNIX operating system internal to Bell Labs. It was developed at the Columbus, Ohio branch and was little-known outside the company. CB UNIX was developed to address deficiencies inherent in Research Unix, notably the lack of interprocess communication and file locking, considered essential for a database management system. Several Bell System operation support system products were based on CB UNIX such as Switching Control Center System. The primary innovations were power-fail restart, line disciplines, terminal types, and IPC features similar to System V's messages and shared memory.