PDP-11

This article is about the PDP–11 series of minicomputers. For the PDP–11 processor architecture, see PDP-11 architecture.
PDP–11
A PDP–11/40 CPU is at the bottom, with a TU56 dual DECtape drive installed above it.
DeveloperDigital Equipment Corporation
Product familyProgrammed Data Processor
TypeMinicomputer
Release date1970; 54 years ago (1970)
Lifespan1970–1997
Discontinued1997; 27 years ago (1997)
Units soldaround 600,000
Operating systemBATCH-11/DOS-11, DSM-11, IAS, P/OS, RSTS/E, RSX-11, RT-11, Ultrix-11, Seventh Edition Unix, SVR1, 2BSD
PlatformDEC 16-bit
SuccessorVAX-11

The PDP–11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the late 1990s, one of a set of products in the Programmed Data Processor (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.[1][2]

The PDP–11 included a number of innovative features in its instruction set and additional general-purpose registers that made it easier to program than earlier models in the PDP series. Further, the innovative Unibus system allowed external devices to be more easily interfaced to the system using direct memory access, opening the system to a wide variety of peripherals. The PDP–11 replaced the PDP–8 in many real-time computing 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 microprocessors including the Intel x86[1] and the Motorola 68000. The design features of PDP–11 operating systems, and other operating systems from Digital Equipment, influenced the design of 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,[3] albeit not originally by design.[4]

An effort to expand the PDP–11 from 16- to 32-bit addressing led to the VAX-11 design, which took part of its name from the PDP–11.

  1. ^ a b Supnik, Bob (August 31, 2004). "Simulators: Virtual Machines of the Past (and Future)". ACM Queue. 2 (5): 52–58. doi:10.1145/1016998.1017002. S2CID 20078751.
  2. ^ Rose, Frank (1985). Into the Heart of the Mind: An American Quest for Artificial Intelligence. p. 37. ISBN 9780394741031. Archived from the original on 2024-07-01. Retrieved 2020-07-19.
  3. ^ Bakyo, John. "Section Three: The Great Dark Cloud Falls: IBM's Choice". Great Microprocessors of the Past and Present (V 13.4.0). Part I: DEC PDP-11, benchmark for the first 16/32 bit generation. (1970). Archived from the original on 2023-04-30. Retrieved 2023-04-30.
  4. ^ Ritchie, Dennis M. (April 1993). "The Development of the C Language". In Thomas J. Bergin, Jr.; Richard G. Gibson, Jr. (eds.). History of Programming Languages-II. Second History of Programming Languages conference. Cambridge, MA: ACM Press (New York) and Addison-Wesley (Reading, Mass). ISBN 0-201-89502-1. Archived from the original on 2015-06-11. Retrieved 2023-04-30.