VAX is a line of computers developed by Digital Equipment Corporation (DEC) in the mid-1970s. The VAX-11/780, introduced on October 25, 1977, was the first of a range of popular and influential computers implementing the VAX instruction set architecture (ISA).
A 32-bit system with a complex instruction set computer (CISC) architecture based on DEC's earlier PDP-11, VAX ("virtual address extension") was designed to extend or replace DEC's various Programmed Data Processor (PDP) ISAs. The VAX architecture's primary features were virtual addressing (for example demand paged virtual memory) and its orthogonal instruction set.
VAX has been perceived as the quintessential CISC ISA, with its very large number of assembly-language-programmer-friendly addressing modes and machine instructions, highly orthogonal architecture, and instructions for complex operations such as queue insertion or deletion and polynomial evaluation.[1] It is historically one of the most studied and commented-on ISA's in computer history.[2]
VAX was succeeded by the DEC Alpha instruction set architecture.
