PDP-11

The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years. The PDP-11 had several uniquely innovative features, and was easier to program than its predecessors with its use of general registers. Its successor in the mid-range minicomputer niche was the 32-bit VAX-11.

Design features of the PDP-11 influenced the design of microprocessors such as the Motorola 68000; design features of its operating systems, as well as other operating systems from Digital Equipment, influenced the design of other operating systems such as CP/M and hence also MS-DOS. The first officially named version of Unix ran on the PDP-11/20 in 1970. It is commonly stated that the C programming language took advantage of several low-level PDP-11–dependent programming features, albeit not originally by design.