PDP-11

The PDP–11 is a series of <a href="/facts/16-bit_computing/bTGS44Ne">16-bit</a> <a href="/facts/Minicomputer/g8hvpQxe">minicomputers</a> originally sold by <a href="/facts/Digital_Equipment_Corporation/ztxs6keA">Digital Equipment Corporation</a> (DEC) from 1970 into the late 1990s, one of a set of products in the <a href="/facts/Programmed_Data_Processor/Rgwfdqjy">Programmed Data Processor</a> (PDP) series. In total, around 600,000 PDP-11s of all models were sold, making it one of DEC's most successful product lines. The PDP-11 is considered by some experts to be the most popular minicomputer.
The PDP–11 included a number of innovative features in its <a href="/facts/Instruction_set/8p8vwUeE">instruction set</a> and additional general-purpose <a href="/facts/Hardware_register/V1roVh0p">registers</a> that made it easier to program than earlier models in the PDP series. Further, the innovative <a href="/facts/Unibus/HGEzSfuY">Unibus</a> system allowed external devices to be more easily interfaced to the system using <a href="/facts/Direct_memory_access/DWuVgclV">direct memory access</a>, opening the system to a wide variety of <a href="/facts/Peripheral/3lEBPE14">peripherals</a>. The PDP–11 replaced the <a href="/facts/PDP-8/udvrynE8">PDP–8</a> in many <a href="/facts/Real-time_computing/p9HxgL4L">real-time computing</a> applications, although both product lines lived in parallel for more than 10 years. The ease of programming of the PDP–11 made it popular for general-purpose computing.
The design of the PDP–11 inspired the design of late-1970s <a href="/facts/Microprocessor/Fx9CaQht">microprocessors</a> including the <a href="/facts/Intel/SMF0gJJX">Intel</a> <a href="/facts/X86/Kypq5fgu">x86</a> and the <a href="/facts/Motorola_68000/3p2wt2D6">Motorola 68000</a>. The design features of PDP–11 operating systems, and other operating systems from Digital Equipment, influenced the design of operating systems such as <a href="/facts/CP%2fM/n5rTgXdC">CP/M</a> and hence also <a href="/facts/MS-DOS/fVrrz1uN">MS-DOS</a>. The first officially named version of <a href="/facts/Unix/0pNL2seI">Unix</a> ran on the PDP–11/20 in 1970. It is commonly stated that the <a href="/facts/C_(programming_language)/Ky2No763">C programming language</a> took advantage of several low-level PDP–11–dependent programming features, albeit not originally by design.
An effort to expand the PDP–11 from 16- to 32-bit addressing led to the <a href="/facts/VAX-11/prkm7jvA">VAX-11</a> design, which took part of its name from the PDP–11.

PDP-11 open-in-new

PDP-11