AT&T Computer Systems is the generic name for American Telephone & Telegraph's unsuccessful attempt to compete in the computer business. In return for divesting the local Bell Operating Companies (Baby Bells), AT&T was allowed to have an unregulated division to sell computer hardware and software. The company made the 3B series computers. Background In the early 1980s, the Bell Labs Processor Division had developed several computer ranges, primarily for internal Bell System use: the 3B20D ("D" for Duplex); the commercial simplex version 3B20S, which competed with the DEC VAX; and the 3B5 and 3B15 computers for billing and telecom switching control applications, which used the world's first 32-bit microprocessor, the Bellmac 32A. Formation post-divestiture After divestiture of the Bell System on January 1, 1984, AT&T was required to put its computer business into a fully separated subsidiary called AT&T Information Systems (ATTIS, without the ampersand or hyphen). Software was developed in New Jersey (at Murray Hill, Summit, Holmdel, and Piscataway), and software, hardware, and system solutions were developed in Naperville and Lisle, Illinois. After a couple of years of court hearings, AT&T was allowed to pull the business back into the mainstream corporate organization, and it was renamed AT&T Data Systems Group, which had three divisions: Computer, Terminals (the Teletype Corporation of Skokie, Illinois), and Printers. AT&T Data Systems Group was announced to the public in 1991. In 1992 the Terminals division was sold to Memorex-Telex, and the Printer division, which had only bought OEM equipment from Genicom, was phased out. By the mid-1990s, this left only AT&T Computer Systems. AT&T Computer Systems (abbreviated AT&T-CS) was the home of the UNIX System V operating system, originally developed in the Bell Labs Research Division. The important System V Interface Definition (SVID) was written, attempting to standardize the various flavors of Unix, and define the official interfaces which made up a Unix operating system. In 1988, AT&T announced its intent to buy up to a 20% stake in Sun Microsystems, a company then best known for making high-end Unix workstations. Upset at their academic-minded supplier (Bell Labs) now turned competitor (AT&T-CS), the "Gang of Seven" Unix system vendors founded the Open Software Foundation (OSF), each contributing source code from their UNIX SVR3 versions. AT&T founded the UNIX International organization as a response to the OSF. But by the late 1980s, AT&T had almost given up, sold most of its stake in Sun,