VAX is a 32-bit computing architecture that supports an orthogonal machine language and virtual addressing (i.e. demand paged virtual memory). It was developed in the mid-1970s by Digital Equipment Corporation (DEC). DEC was later purchased by Compaq, which in turn was later purchased by Hewlett-Packard.
The VAX has been perceived as the quintessential CISC processing architecture, with its very large number of addressing modes and machine instructions, including instructions for such complex operations as queue insertion/deletion and polynomialIn mathematics polynomial functions or polynomials are an important class of simple and smooth functions. Simple means they are constructed using only multiplication and addition. Smooth means they are infinitely differentiable, i. they have derivatives o evaluation.
1 The name
"VAX" was originally an acronym for Virtual Address eXtension, because the VAX was seen as a 32-bit extension of the older 16-bitIn computer science, 16-bit is an adjective used to describe integers that are at most two bytes wide, or to describe CPU architectures based on registers, address buses, or data buses of that size. Prominent 16-bit processors include the Intel 8086, Inte PDP-11The PDP-11 was a 16-bit minicomputer sold by Digital Equipment Corp. in the 1970s and 1980s. The PDP-11 was a successor to DEC's PDP-8 computer in the PDP series of computers. It had several uniquely innovative features, and was easier to program because; early versions of the VAX processor implemented a "compatibility mode" that
emulated many of the PDP-11's instructions. Later versions offloaded the compatibility mode and some of the less used CISC instructions to microcode or emulation in the operating system software.
VAX is also a brand of wet-dry vacuum cleanerA vacuum cleaner is a device that uses an air pump to suck up dust and other small particles of dirt, usually from carpeted floors. Most homes with carpeted floors possess a domestic model for cleaning. The dirt is collected by a filtering system or a cycs, invented in the 1970s by Alan Brazier . The advertising slogan "Nothing sucks like a Vax" was often applied wryly by users of VAX computers.
There are varied accounts of the legal interactions between DEC and the VAX corporation over the use of this trademark. The terms of the settlement involved a non-competition agreement between the companies—DEC would not move into household appliances and the VAX corporation would stay out of computing. In the historical context, when many industrial electronics firms were involved in development of large computer systems, this seemed much less ridiculous than today.
2 Operating systems
VAX computer systems (informal plural is VAXen) could run several operating systems, usually BSD UNIX or DECs VAX/VMS (but even Linux is running on some VAXen nowadays). The VAX architecture and VMS operating system were "engineered concurrently" to take maximum advantage of each other, including sophisticated clustering, initially over special CI buses ("Computer Interconnect") but later over Ethernet as well.
