VAX, also known as Virtual Address Extension, is the name of a 32-bit ISA (instruction set architecture), and a line of computers based on that architecture. It was designed by DEC in the mid-1970s to better execute programs written in high-level programming languages. It replaced the previous PDP ISA, and ran the VAX/VMS operating system, also developed by DEC.
The first VAX computer was the VAX-11/780 (shown right), released on October 25, 1977. The entire line of computers was extremely popular in the 1980s in corporate, scientific, and educational institutions.
- Virtual memory mapping.
- New addressing modes, including literal, post-decrement, pre-decrement, register deferred, post-increment deferred, pre decrement deferred as well as byte, word, and long displacement.
- Four hardware-implemented privilege modes: kernel, executive, supervisor, and user.
- Updated processor status registers.