Editing AT&T Computer Systems (section)

== 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 [[Digital Equipment Corporation|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 32|Bellmac 32A]].