What is "pdp-11"

The PDP-11 is 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 had several uniquely innovative features, and was easier to program than its predecessors through the additional general-purpose registers. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years. In total, around 600,000 PDP-11s of all models were sold, making it one of DEC's most successful product lines. Its successor in the mid-range minicomputer niche was the 32-bit VAX-11, named as a nod to the PDP-11's popularity.

The PDP-11 is considered by some experts to be the most popular minicomputer ever. Design features of the PDP-11 influenced the design of most late-1970s computer systems including the Intel x86 and the Motorola 68000.

Design features of PDP-11 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. For a decade, the PDP-11 was the smallest system that could run Unix; the first officially named version 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.