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.

Read more about PDP-11:  History, LSI-11, Decline, Models, Peripherals, Use

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PDP-11 - Use
... The PDP-11 family of computers was used for many purposes ... An example of such use of PDP-11s was the management of the packet switched network Datanet 1 ... Navy used a PDP-11/34 to control its Multi-station Spatial Disorientation Device, a simulator used in pilot training, until 2007, when it was replaced by a PC-based ...
Digital Equipment Corporation - History - PDP-11
... The PDP-11 16-bit computer was designed in a crash program by Harold McFarland, Gordon Bell, Roger Cady, and others ... One of his simpler designs became the PDP-11, although when they first viewed the proposal, management was not impressed and almost cancelled it ... A major advance in the PDP-11 design was Digital's Unibus, which supported all peripherals through memory mapping ...