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A modified PDP-7 under restoration in Oslo, Norway
Manufacturer Digital Equipment Corporation
Product family Programmed Data Processor
Type Minicomputer
Release date1965;56 years ago (1965)
Introductory priceUS$72,000(equivalent to $584,135 in 2019)
Units sold120 [1] [2]
Units shipped120 [2]
Operating system DECsys, Unix (as ‘’Unics’’)
Memory4K words(9.2 KB) (expandable up to 64K words(144 KB).) [1]
StoragePaper-tape and dual transport DECtape drives (type 555)
Platform DEC 18-bit
Predecessor PDP-4
Successor PDP-9
Modified PDP-7 under restoration in Oslo, Norway Pdp-7-oslo-2004.jpeg
Modified PDP-7 under restoration in Oslo, Norway
PDP-7 at living computer museum DEC PDP-7.jpg
PDP-7 at living computer museum

The PDP-7 was a minicomputer produced by Digital Equipment Corporation as part of the PDP series. Introduced in 1964, [3] :p.8 [4] shipped since 1965, it was the first [5] to use their Flip-Chip technology. With a cost of US$72,000, it was cheap but powerful by the standards of the time. The PDP-7 is the third of Digital's 18-bit machines, with essentially the same instruction set architecture as the PDP-4 and the PDP-9.



The PDP-7 was the first wire-wrapped PDP. The computer had a memory cycle time of 1.75 µs and an add time of 4 µs. I/O included a keyboard, printer, paper-tape and dual transport DECtape drives (type 555). [6] The standard memory capacity was 4K words(9 KB) but expandable up to 64K words(144 KB). [1]

The PDP-7 weighed about 1,100 pounds (500 kg). [7]


DECsys, the first operating system for DEC's 18-bit computer family (and DEC's first operating system for a computer smaller than its 36-bit timesharing systems), was introduced in 1965. It provided an interactive, single user, program development environment for Fortran and assembly language programs. [8]

In 1969, Ken Thompson wrote the first UNIX system in assembly language on a PDP-7, [9] then named Unics as a pun on Multics, as the operating system for Space Travel , a game which requires graphics to depict the motion of the planets. A PDP-7 was also the development system used during the development of MUMPS at MGH in Boston a few years earlier.


The PDP-7 was described as "highly successful." [10] A combined total of 120 of the PDP-7 and PDP-7A were sold. [3] :p.8 A DEC publication states that the first units shipped to customers in November 1964.

Eleven systems were shipped to the UK. [5]


At least four PDP-7s were confirmed to still exist as of 2011 [5] and a fifth was discovered in 2017. [11]

A PDP-7A (S#115) was under restoration in Oslo, Norway; [12] a second PDP-7A (S#113) previously located at the University of Oregon in its Nuclear Physics laboratory is now at the Living Computer Museum in Seattle, Washington and is completely restored to running condition after being disassembled for transport; [13] Another PDP-7 (S#47) is known to be in the collection of Max Burnet near Sydney, Australia, a fourth PDP-7 (S#33) is in storage at the Computer History Museum in Mountain View, California and a fifth PDP-7 (S#129) belonging to Fred Yerian is also located at the Museum, and has been demonstrated running Unix version 0 and compiling a B program. [11]

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Minicomputer Mid-1960s–late-1980s class of smaller computers

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  1. 1 2 3 "PDP-7 Definition". The Linux Information Project. September 27, 2007.
  2. 1 2 "1964 — PDP-7". DIGITAL Computing Timeline via Microsoft. Ultimately, 120 PDP-7s were produced and sold.
  3. 1 2 "Digital Equipment Corporation - 1957 to the present" (PDF).
  4. "across the editor's desk: COMPUTING AND DATA PROCESSING NEWSLETTER - PDP-7 ANNOUNCED BY DIGITAL" (PDF). Computers and Automation. XIII (7): 45. July 1964. Retrieved September 5, 2020.
  5. 1 2 3 Tore Sinding Bekkedal (2009). "Digital Equipment Corporation PDP-7". soemtron.org.
  6. "Pdp-7". reference.com Computing Dictionary. Archived from the original on June 16, 2013.
  7. "PDP-7 documents". www.bitsavers.org. PDP-7_Maint.pdf, p. 1-14 (32).
  8. Supnik, Bob (June 19, 2006). "Technical Notes on DECsys" (PDF).
  9. Ritchie, Dennis M. "The Development of the C Language".
  10. "RI Computer Museum, DEC PDP-9, System Number 319".
  11. 1 2 "Restoring UNIX v0 on a PDP-7: A look behind the scenes" . Retrieved November 18, 2019.
  12. "Picture album of PDP-7 restoration project". Archived from the original on July 15, 2012. Retrieved June 24, 2005. PDP-7 restoration project located in Oslo, Norway.
  13. "Colloquium Details - The University's 40 year old PDP-7 computer is alive again in Seattle". Archived from the original on March 14, 2012. Retrieved March 2, 2011. University of Oregon's PDP-7 moves to the Living Computer Museum in Seattle, Washington. Alternate host at http://www.soemtron.org/pdp7no113systeminfo.html "January 2011" section.