View source for PDP-1

{{Short description|First computer made by Digital Equipment Corp}}
{{for|the matrix decomposition ''PDP<sup>-1</sup>''|Diagonalizable matrix}}
{{Use mdy dates|date=March 2022}}
{{Infobox computing device
| name = PDP-1
| title = 
| aka = 
| logo = PDP-1 wordmark horizontal.svg
| image = DEC PDP-1 Demo Lab at Mountain View's Computer History Museum.jpg
| caption = PDP-1 exhibit at the [[Computer History Museum]] in [[Mountain View, California]]
| developer = [[Digital Equipment Corporation]]
| manufacturer = 
| family = [[Programmed Data Processor]]
| type = [[Minicomputer]]
| generation = 
| releasedate = {{Start date and age|1959}}
| lifespan = 
| price = {{USD|120000|1959}}
| discontinued = {{End date|1969}}
| unitssold = 
| unitsshipped = 53
| media = [[Punched tape]]
| os = [[BBN Time-Sharing System]], [[Stanford Time Sharing System]];<ref>{{Cite web |date=2022-02-06 |orig-date=1997-08-15 |title=Early Computers at Stanford |url=https://forum-old.stanford.edu/wiki/index.php/Early_Computers_at_Stanford#DEC_PDP-1 |access-date=2024-07-06 |website=[[Stanford University]] |archive-url=https://web.archive.org/web/20230327053505/https://forum-old.stanford.edu/wiki/index.php/Early_Computers_at_Stanford#DEC_PDP-1 |archive-date=2023-03-27}}</ref> most software, including ''Spacewar!'', uses no operating system
| power = 
| soc = 
| cpu = 
| memory = {{nowrap|4K words}} {{nowrap|(9.2 KB)}} [[magnetic-core memory]]
| storage = 
| memory card = 
| display = Type 30 CRT
| graphics = 
| sound = 
| input = 
| controllers = 
| camera = 
| touchpad = 
| connectivity = 
| platform = [[Programmed Data Processor|PDP]] 18-bit
| service = 
| dimensions = 
| weight = {{cvt|1600|lb|kg|order=flip}}
| topgame = 
| compatibility = 
| predecessor = [[TX-0]] and [[TX-2]]
| successor = [[PDP-4]]
| related = 
| website = 
| CPUspeed = 187 kHz
}}
The '''PDP-1''' ('''Programmed Data Processor-1''') is the first [[computer]] in [[Digital Equipment Corporation]]'s [[Programmed Data Processor|PDP]] series and was first produced in 1959. It is known for being the most important computer in the creation of [[hacker culture]] at the [[Massachusetts Institute of Technology]], [[Bolt, Beranek and Newman]], and elsewhere.<ref>{{Cite web |title=Computer History Museum PDP-1 Restoration Project – Introduction |url=http://www.computerhistory.org/pdp-1/introduction/ |url-status=live |archive-url=https://web.archive.org/web/20220316020556/https://www.computerhistory.org/pdp-1/introduction/ |archive-date=2022-03-16 |access-date=2011-04-06 |website=[[Computer History Museum]] |language=en}}</ref> The PDP-1 is the original hardware for one of the [[Early history of video games|first video games]], [[Steve Russell (computer scientist)|Steve Russell]]'s 1962 game ''[[Spacewar!]].''<ref name="CED">{{Cite web |title=1960: DEC PDP-1 Precursor to the Minicomputer |url=http://www.cedmagic.com/history/dec-pdp-1.html |url-status=live |archive-url=https://web.archive.org/web/20220103020252/http://www.cedmagic.com/history/dec-pdp-1.html |archive-date=2022-01-03 |access-date=2008-12-04 |website=CED Magic |language=en}}</ref>

==Description==
[[File:Steve Russell and PDP-1.png|thumb|right|PDP-1 at the [[Computer History Museum]] with [[Steve Russell (computer scientist)|Steve Russell]], creator of ''[[Spacewar (video game)|Spacewar!]]'' The large cabinet houses the processor. The main control panel is just above the desk, the paper tape reader is above it (metallic), and the output of the Teletype model BRPE paper tape punch above that (vertical slot). A storage tray for eight fanfold paper tapes is attached to the top panel. At the left is the [[IBM Electric typewriter|IBM Model B]] [[typewriter]] modified by Soroban Engineering, and the Type 30 CRT display is to the far right.]]

The PDP-1 uses an [[18-bit]] [[word (computer architecture)|word]] size and has 4096 words as standard [[main memory]] (equivalent in bit size to 9,216 eight-bit [[byte]]s, but in character size to 12,388 bytes since the system actually divides an 18-bit word into three six-bit characters), upgradable to 65,536 words. The [[magnetic-core memory]]'s cycle time is 5.35 [[microsecond]]s (corresponding roughly to a [[clock speed]] of 187 [[kilohertz]]); consequently most arithmetic instructions take 10.7 microseconds (93,458 operations per second) because they use two memory cycles: the first to fetch the instruction, the second to fetch or store the data word. Signed numbers are represented in [[ones' complement]]. The PDP-1 has computing power roughly equivalent to a 1996 pocket organizer and a little less memory.<ref>{{Cite book |last1=Hafner |first1=Katie |url=https://archive.org/details/wherewizardsstay00haf_vgj/page/85 |title=Where wizards stay up late : the origins of the Internet |last2=Lyon |first2=Matthew |date=1996 |publisher=[[Simon and Schuster]] |isbn=978-0-684-81201-4 |edition=1st Touchstone |location=[[New York City]] |page=85 |lccn=96019533 |oclc=935805191 |ol=23262579M |author-link=Katie Hafner |url-access=registration |via=[[Internet Archive]]}}</ref>

[[File:Dec SYSTEM BUILDING BLOCKS logo.jpg|thumb|A System Building Block, seen end-on]]
[[File:Dec SYSTEM BUILDING BLOCKS 1103.jpg|thumb|System Building Blocks 1103 hex-inverter card]]
[[File:PDP-1 System Building Block No. 4106.jpg|thumb|PDP-1 System Building Block #4106, circa 1963, with a [[Quarter (United States coin)|US quarter]] – note that one transistor (yellow) has been replaced]]

The PDP-1 uses 2,700 [[transistor count|transistors]] and 3,000 diodes.<ref>{{Cite web |title=PDP-1 computer |url=http://www.computerhistory.org/revolution/digital-logic/12/273/1370 |url-status=live |archive-url=https://web.archive.org/web/20210607163900/https://www.computerhistory.org/revolution/digital-logic/12/273/1370 |archive-date=2021-06-07 |access-date=2022-03-23 |website=[[Computer History Museum]] |language=en}}</ref> It is constructed mostly of [[Digital Equipment Corporation|DEC]] 1000-series [[System Module|System Building Blocks]], using [[micro-alloy transistor|micro-alloy]] and [[micro-alloy diffused transistor]]s with a rated switching speed of 5{{nbsp}}MHz. The System Building Blocks are packaged into several [[19-inch rack]]s. The racks are themselves packaged into a single large mainframe case, with a hexagonal control panel containing switches and lights mounted to lie at table-top height at one end of the mainframe. Above the control panel is the system's standard [[input/output]] solution, a [[punched tape]] reader and writer.

The PDP-1 weighs about {{cvt|1600|lb|kg|order=flip}}.<ref>{{Cite web |last=Weik |first=Martin H. |date=March 1961 |title=Programmed Data Processor |url=http://www.ed-thelen.org/comp-hist/BRL61-p.html#PROGRAMMED-DATA-PROCESSOR |url-status=live |archive-url=https://web.archive.org/web/20220321031719/http://www.ed-thelen.org/comp-hist/BRL61-p.html#PROGRAMMED-DATA-PROCESSOR |archive-date=2022-03-21 |access-date=2018-07-06 |website=Ed Thelen's Nike Missile Web Site |series=A Third Survey of Domestic Electronic Digital Computing Systems |language=en}}</ref>

==History==
The design of the PDP-1 is based on the pioneering [[TX-0]] and [[TX-2]] computers, designed and built at [[MIT Lincoln Laboratory]]. [[Ben Gurley|Benjamin Gurley]] was the lead engineer on the project.<ref>{{Cite web |title=Ben Gurley |url=http://www.computerhistory.org/pdp-1/ben-gurley/ |url-status=live |archive-url=https://web.archive.org/web/20210227044243/https://www.computerhistory.org/pdp-1/ben-gurley/ |archive-date=2021-02-27 |access-date=2022-03-23 |website=[[Computer History Museum]] |language=en}}</ref> After showing a prototype at the [[Eastern Joint Computer Conference]] in December 1959, DEC delivered the first PDP-1 to [[BBN Technologies|Bolt, Beranek and Newman]] (BBN) in November 1960,<ref>{{Cite web |title=1960 |url=http://vt100.net/timeline/1960.html |url-status=live |archive-url=https://archive.today/20120716084916/http://vt100.net/timeline/1960.html |archive-date=2012-07-16 |access-date=2022-03-23 |website=DIGITAL Computing Timeline |language=en}}</ref><ref>{{Cite book |last1=Bell |first1=C. Gordon |url={{GBurl|id=SDOoBQAAQBAJ|page=134}} |title=Computer Engineering: A DEC View of Hardware Systems Design |last2=Mudge |first2=J. Craig |last3=McNamara |first3=John E. |date=2014 |publisher=Digital Press |isbn=978-1-4832-2110-6 |pages=123–124, 134–137 |language=en |oclc=900212390 |access-date=June 30, 2024 |archive-date=October 19, 2023 |archive-url=https://web.archive.org/web/20231019081250/https://books.google.com/books?id=SDOoBQAAQBAJ&pg=PA134 |url-status=live }}</ref> and it was formally accepted in early 1961.<ref>{{Cite journal |date=Apr 1961 |title=News of Computers and' Data Processors: Across the Editor's Desk – the First "Programmed Data Processor" Delivered and in Use |url=https://archive.org/details/bitsavers_computersA_6613365/page/n31 |journal=[[Computer magazine#1940s–1950s|Computers and Automation]] |volume=10 |issue=4(B) |page=8B |access-date=2022-03-22 |via=[[Internet Archive]] |language=en}}</ref> In September 1961, DEC donated the PDP-1 to MIT,<ref>{{Cite web |date=1998-04-30 |title=PDP-1 Story |url=http://gordonbell.azurewebsites.net/digital/timeline/pdp-1story.htm |url-status=live |archive-url=https://web.archive.org/web/20220215061817/http://gordonbell.azurewebsites.net/digital/timeline/pdp-1story.htm |archive-date=2022-02-15 |access-date=2022-03-23 |website=[[Gordon Bell]] |language=en}}</ref> where it was placed in the room next to its ancestor, the TX-0 computer,<ref>{{Cite AV media |url=https://www.youtube.com/watch?v=J8zU8WQO-PY |title=The Mouse That Roared: PDP-1 Celebration Event Lecture |date=2006-05-15 |publisher=[[Computer History Museum]] |time=32:48 panel starts, 43:55 and 47:00 first prototype Dec 1959, 52:40 PDP-1 donation in Sep 1961, 53:46 PDP-1 next to TX-0 in 1961 (about 3 min) |time-caption=Citation timestamps |access-date=2022-03-22 |archive-url=https://web.archive.org/web/20220323014417/https://www.youtube.com/watch?v=J8zU8WQO-PY |archive-date=2022-03-23 |url-status=live |lang=en}}</ref> which was by then on indefinite loan from Lincoln Laboratory.

In this setting, the PDP-1 quickly replaced the TX-0 as the favorite machine among the budding [[hacker culture]], and served as the platform for a long list of computing innovations. This list includes one of the earliest video games, ''[[Spacewar (video game)|Spacewar!]]'',<ref name="CED" /> the first [[text editor]], the first [[word processor]], the first interactive [[debugger]], one of the very earliest time-sharing systems ([[BBN Time-Sharing System]]), and some of the earliest computerized music.<ref>{{Cite web |last1=Strebe |first1=Judith A. |last2=Kim |first2=Rebekah |year=2006 |title=Guide to the Collection of Digital Equipment Corporation PDP-1 Computer Materials |url=http://archive.computerhistory.org/resources/access/text/finding-aids/102660913-PDP-1/102660913-PDP-1.pdf |url-status=live |archive-url=https://web.archive.org/web/20210828023933/http://archive.computerhistory.org/resources/access/text/finding-aids/102660913-PDP-1/102660913-PDP-1.pdf |archive-date=2021-08-28 |access-date=2022-03-23 |website=[[Computer History Museum]] |language=en}}</ref> The [[ARPANET]] [[Interface Message Processor|IMP]] software was composed, edited, and assembled on BBN’s PDP-1d computer using a modified assembler, highlighting the PDP-1's role in the early development of the ARPANET.<ref>{{Cite journal |last=David Walden and the “IMP Software Guys” |date=2014 |title=The Arpanet IMP Program: Retrospective and Resurrection |url=https://www.walden-family.com/impcode/imp-code.pdf |journal=IEEE Annals of the History of Computing}}</ref>

At the Computer History Museum [[TX-0]] alumni reunion in 1984, [[Gordon Bell]] said DEC's products developed directly from the [[TX-2]], the successor to the TX-0 which had been developed at what Bell thought was a bargain price at the time, about {{USD|3 million}}. At the same meeting, [[Jack Dennis]] said Ben Gurley's design for the PDP-1 was influenced by his work on the TX-0 display.
<ref>{{Cite journal |date=Spring 1984 |title=The TX-0: Its Past and Present |url=http://tcm.computerhistory.org/reports/TCMReportSpring1984.pdf |journal=The Computer Museum Report |issue=8 |archive-url=https://web.archive.org/web/20150908042855/http://tcm.computerhistory.org/reports/TCMReportSpring1984.pdf |archive-date=2015-09-08 |access-date=2022-03-23 |language=en}}</ref>

The PDP-1 sold in basic form for {{currency|120000|USD}} (equivalent to {{currency|{{inflation|US|120000|1961}}|USD}} in {{inflation/year|US}}).<ref name="NGen23">{{Cite magazine |date=November 1996 |title=The Great Videogame Swindle? |url=https://archive.org/details/NextGeneration23Nov1996P2/page/n87 |magazine=[[Next Generation (magazine)|Next Generation]] |publisher=[[Imagine Media]] |issue=23 |pages=64–68, 211–229 |access-date=2022-03-22 |via=[[Internet Archive]] |lang=en}}</ref> BBN's system was quickly followed by orders from [[Lawrence Livermore National Laboratory|Lawrence Livermore]] and [[Atomic Energy of Canada Limited|Atomic Energy of Canada]] (AECL), and eventually 53 PDP-1s were delivered until production ended in 1969.<ref>{{Cite book |last=Digital Equipment Corporation |url=http://gordonbell.azurewebsites.net/digital/dec%201957%20to%20present%201978.pdf |title=Digital Equipment Corporation: Nineteen Fifty-Seven to the Present |publisher=DEC Press |year=1978 |page=3 |author-link=Digital Equipment Corporation |access-date=2022-03-23 |archive-url=https://archive.today/20220323021612/http://gordonbell.azurewebsites.net/digital/dec%201957%20to%20present%201978.pdf |archive-date=2022-03-23 |url-status=live |language=en}}</ref><ref>{{Cite encyclopedia |title=History of Computing:An Encyclopedia of the People and Machines that Made Computer History |date=February 2001 |publisher=Lexikon Services |url=https://openlibrary.org/books/OL11565276M/History_of_Computing |editor-last=Grenia |editor-first=Mark W. |language=en |isbn=978-0-944601-78-5 |ol=11565276M |via=[[Open Library]] |access-date=March 23, 2022 |archive-date=March 23, 2022 |archive-url=https://web.archive.org/web/20220323051327/https://openlibrary.org/books/OL11565276M/History_of_Computing |url-status=live }}</ref> All of these machines were still being actively used in 1970, and several were eventually saved. MIT's example was donated to [[The Computer Museum, Boston]], and from there ended up at the [[Computer History Museum]] (CHM). A late version of ''Spacewar!'' on paper tape was still tucked into the case. PDP-1 #44 was found in a barn in [[Wichita, Kansas]] in 1988, apparently formerly owned by one of the many aviation companies in the area, and rescued for the Digital Historical Collection, also eventually ending up at the CHM.<ref>{{Cite web |last=Bergin |first=Thomas |title=Digital Equipment Corporation |url=https://slidetodoc.com/digital-equipment-corporation-thomas-j-bergin-computer-history/ |url-status=live |archive-url=https://archive.today/20220323024600/https://slidetodoc.com/digital-equipment-corporation-thomas-j-bergin-computer-history/ |archive-date=2022-03-23 |access-date=2022-03-22 |website=SlideToDoc |language=en}}</ref> AECL's computer was sent to [[Science North]], but was later scrapped.

The launch of the PDP-1 marked a radical shift in the philosophy of computer design: it is the first commercial computer that focuses on interaction with the user rather than just the efficient use of computer cycles.<ref>{{Cite web |title=DEC PDP-1 Collection |url=http://www.computerhistory.org/collections/decpdp-1/ |url-status=dead |archive-url=https://web.archive.org/web/20180714144435/http://www.computerhistory.org/collections/decpdp-1/ |archive-date=2018-07-14 |access-date=2013-03-06 |website=[[Computer History Museum]]}}</ref>

The first ever reference to malicious [[security hacker|hacking]] is '[[phreaking|telephone hackers]]' in [[Massachusetts Institute of Technology|MIT]]'s student newspaper, ''[[The Tech (newspaper)|The Tech]]'', of hackers tying up the lines with [[Harvard University|Harvard]], configuring the PDP-1 to make free calls, [[war dialing]] and accumulating large phone bills.<ref>{{Cite web |last=Press |first=Gil |date=2011-11-20 |title=Hacking and Blue Boxes |url=https://infostory.com/2011/11/20/hacking-and-blue-boxes/ |url-status=live |archive-url=https://web.archive.org/web/20210418083353/https://infostory.com/2011/11/20/hacking-and-blue-boxes/ |archive-date=2021-04-18 |website=The Story of Information}}</ref><ref>{{Cite news |last=Duarte |first=Gustavo |date=2008-08-27 |title=First Recorded Usage of "Hacker" |work=Many But Finite |url=http://duartes.org/gustavo/blog/post/first-recorded-usage-of-hacker/ |url-status=live |access-date=2022-03-23 |archive-url=https://web.archive.org/web/20220221221433/https://manybutfinite.com/post/first-recorded-usage-of-hacker/ |archive-date=2022-02-21 |language=en}}</ref><ref>{{Cite news |last=Lichstein |first=Henry |date=1963-11-20 |title=Telephone Hackers Active |volume=83 |page=1 |work=[[The Tech (newspaper)|The Tech]] |issue=24 |url=http://tech.mit.edu/V83/PDF/V83-N24.pdf |url-status=live |access-date=2022-03-23 |archive-url=https://web.archive.org/web/20220216083012/http://tech.mit.edu/V83/PDF/V83-N24.pdf |archive-date=2022-02-16 |language=en}}</ref>

==Peripherals==
[[File:PDP-1.jpg|thumb|PDP-1 Type 30 point-mode CRT display and console typewriter, with processor frame in background]]

The PDP-1 uses [[Continuous stationery|fanfold]] punched [[paper tape]] as its primary storage medium.<ref name="NGen23" /> Unlike [[punched card]] decks, which could be sorted and re-ordered, paper tape is tedious to physically edit. This inspired the creation of text-editing programs such as [[Expensive Typewriter]] and [[TECO (text editor)|TECO]]. Because it is equipped with online and offline printers that were based on [[IBM]] electric [[typewriter]] mechanisms, it is capable of what, in 1980s terminology, would be called "[[Letter-quality printer|letter-quality printing]]" and therefore inspired [[TJ-2]], arguably the first [[word processor]].

The console typewriter, known as the ''Computeriter'', was provided by [[Soroban Engineering]]. It is an adapted [[IBM Electric typewriter|IBM Model B Electric typewriter]] mechanism, modified by the addition of switches to detect key presses, and [[solenoid]]s to activate the [[Typewriter|typebars]]. It uses a traditional typebar mechanism, not the "golfball" [[IBM Selectric typewriter]] mechanism, which was not introduced until the next year. Lettercase is selected by raising and lowering the massive type basket. The Soroban is equipped with a two-color inked ribbon (red and black), and the interface allows color selection. Programs commonly use color-coding to distinguish user input from machine responses. The Soroban mechanism is unreliable and prone to jamming, particularly when shifting case or changing ribbon color.<ref>{{cite manual |url=http://bitsavers.informatik.uni-stuttgart.de/pdf/soroban/Soroban_Computeriter_Decoder_and_Power_Unit_Adjustment_and_Lubrication_Procedures_Feb1961.pdf |title=Adjustment and lubrication procedures for decoder and power unit of the computeriter |publisher=Soroban |year=1963 |via=Bitsavers}}</ref><ref>{{cite manual |url=https://telcontar.net/KBK/Soroban/docs/Soroban%20Computeriter%20Coder%20Unit%20Technical%20Manual%20%28March%201963%29.pdf |title=Operation and service with illustrates parts breakdown for coder unit models EC and ETC computeriter |publisher=Soroban |date=March 1963 |via=Telcontar.net}}</ref><ref>{{cite web |url=https://telcontar.net/KBK/Soroban/ |title=Soroban Engineering |website=Telcontar.net |date=2024-01-24 |access-date=2024-08-17}}</ref>

Offline devices are typically [[Friden Flexowriter]]s that have been specially built to operate with the FIO-DEC character coding used by the PDP-1. Like the console typewriter, these are built around a typing mechanism that is mechanically the same as an [[IBM Electric typewriter]].<ref>{{Cite web |last=Mast |first=Bob |date=1998-11-24 |title=From: Bob Mast |url=http://www.blinkenlights.com/classiccmp/friden/bmast.txt |url-status=live |archive-url=https://web.archive.org/web/20220102231005/http://www.blinkenlights.com/classiccmp/friden/bmast.txt |archive-date=2022-01-02 |access-date=2022-03-22 |website=Blinkenlights Archæological Institute |language=en |quote=The Flexowriter was first manufactured by IBM, during WWII, to be used as an automatic letter writer. After the war several [[IBM]]ers bought the rights and formed Commercial Controls, Inc. They manufactured same in the old [[IBM Selectric typewriter]] building in Rochester NY. In the late fifties, [[Friden, Inc.|Friden]] bought Commercial Controls.}}</ref> However, Flexowriters are highly reliable and were often used for long unattended printing sessions. Flexowriters have electromechanical paper tape punches and readers which operate synchronously with the typewriter mechanism. Typing rates are about ten characters per second. A typical PDP-1 operating procedure is to output text to punched paper tape using the PDP-1's "high speed" (60-character-per-second) Teletype model BRPE punch, then to hand carry the tape to a Flexowriter for offline printing.

In later years, [[DECtape]] drives were added to some PDP-1 systems, as a more convenient method of backing up programs and data, and to enable early [[time-sharing]].  This latter application usually requires a secondary storage medium for swapping programs and data in and out of core memory, without requiring manual intervention.  For this purpose, DECtapes are far superior to paper tapes, in terms of reliability, durability, and speed.  Early [[hard disk]]s were expensive and notoriously unreliable;  if available and working, they are used primarily for speed of swapping, and not for permanent file storage.

===Graphics display===
The Type 30 Precision [[CRT display]] is a point plotting display device capable of addressing 1024 by 1024 addressable locations at a rate of 20,000 points per second.<ref name="DECmanual">{{Cite book |url=http://www.bitsavers.org/pdf/dec/pdp1/F15D_PDP1_Handbook_Oct63.pdf |title=PDP-1 Handbook |publisher=[[Digital Equipment Corporation]] |year=1963 |pages=33–36 |access-date=2022-03-22 |archive-url=https://web.archive.org/web/20210828035149/http://www.bitsavers.org/pdf/dec/pdp1/F15D_PDP1_Handbook_Oct63.pdf |archive-date=2021-08-28 |url-status=live |via=[[Computer History Museum#Software|Bitsavers]] |language=en}}</ref> A special "Display One Point On CRT" instruction is used to build up images, which have to be refreshed many times per second.<ref name="DECmanual" /> The CRT, which was originally developed for use in radar, is {{convert|16|in|cm}} in diameter and uses a long-persistence [[Phosphor#Standard phosphor types|P7 phosphor]].<ref name="BickleyVid">{{Cite AV media |url=https://www.youtube.com/watch?v=1EWQYAfuMYw |title=Lyle Bickley explains the PDP-1 (and we play the original Spacewar!) |date=2017-05-02 |last=CuriousMarc |access-date=2018-04-07 |archive-url=https://ghostarchive.org/varchive/youtube/20211211/1EWQYAfuMYw |archive-date=2021-12-11 |url-status=live |via=[[YouTube]]}}{{cbignore}}</ref> A [[light pen]] can be used with the Type 30 to pick points on the display. An optional character generator and hardware for line and curve generation are available.<ref name="DECmanual" />

==Computer music==
MIT hackers also used the PDP-1 for playing music in four-part harmony, using some special hardware – four [[Flip-flop (electronics)|flip-flop]]s directly controlled by the processor (the audio signal is filtered with simple [[RC filter]]s). Music was prepared via [[Peter Samson]]'s ''[[Harmony Compiler]]'', a sophisticated text-based program with some features specifically oriented toward the efficient coding of [[baroque music]]. Several hours of music were prepared for it, including Bach [[fugue]]s, all of Mozart's ''[[Eine kleine Nachtmusik]]'', the ''[[Ode to Joy]]'' movement concluding Beethoven's [[Symphony No. 9 (Beethoven)|''Symphony No. 9'']], Christmas carols, and numerous popular songs.

==Current status==
[[File:PDP-1 control board.jpg|thumb|300px|right|PDP-1 control panel]]

Only three PDP-1 computers are still known to exist, and all three are in the collection of the [[Computer History Museum]] (CHM).  One is the prototype formerly used at MIT, and the other two are production PDP-1C machines.  One of the latter, serial number 55 (the last PDP-1 made) has been restored to working order, is on exhibit, and is demonstrated on two Saturdays every month. The demonstrations include:

* the game ''[[Spacewar (video game)|Spacewar!]]''
* graphics demonstrations such as Snowflake
* playing music

Software simulations of the PDP-1 exist in [[SIMH]] and [[MESS]], hardware recreation through [[FPGA]] exists for the [[MiSTer]] project as well, and binary image of paper tapes of the software exist in the bitsavers.org archives.<ref>{{Cite web |title=Index of /bits/DEC/pdp1/papertapeImages |url=http://bitsavers.org/bits/DEC/pdp1/papertapeImages |url-status=live |archive-url=https://web.archive.org/web/20220107215435/http://bitsavers.org/bits/DEC/pdp1/papertapeImages/ |archive-date=2022-01-07 |access-date=2022-03-16 |language=en |via=[[Computer History Museum#Software|Bitsavers]]}}</ref>

== See also ==
*[[History of computers]]
*[[History of computer science]]
*''[[Spacewar (video game)|Spacewar!]]''
*[[Tech Model Railroad Club]]
*[[Timeline of computing]]

==Notes==
{{reflist}}

==External links==
{{Commons category}}
* {{Cite web |last=Čavrak |first=Hrvoje |date=2019-10-27 |title=FPG-1 is a PDP-1 implementation in FPGA |url=https://github.com/hrvach/fpg1 |url-status=live |archive-url=https://web.archive.org/web/20211009180308/https://github.com/hrvach/fpg1 |archive-date=2021-10-09 |access-date=2022-03-23 |website=[[GitHub]] |language=en}}
* {{Cite web |title=DEC PDP-1 |url=http://www.dbit.com/~greeng3/pdp1/ |url-status=live |archive-url=https://web.archive.org/web/20110514104715/http://www.dbit.com/~greeng3/pdp1/ |archive-date=2011-05-14 |access-date=2022-03-23 |website=D Bit |language=en}}
* {{YouTube|id=9qMrmgo1HnQ|title=DEC PDP-1 music}}
* {{Cite web |title=Index of /pdf/dec/pdp1 |url=http://www.bitsavers.org/pdf/dec/pdp1/ |url-status=live |archive-url=https://web.archive.org/web/20220323042242/http://www.bitsavers.org/pdf/dec/pdp1/ |archive-date=2022-03-23 |access-date=2022-03-22 |website=[[Computer History Museum#Software|Bitsavers]] |language=en}}
* {{Cite AV media |url=https://www.flickr.com/photos/llnl/4885808490/ |title=PDP-1 |date=2006-11-13 |publisher=[[Lawrence Livermore National Laboratory]] |access-date=2022-03-23 |archive-url=https://web.archive.org/web/20210309003017/https://www.flickr.com/photos/llnl/4885808490/ |archive-date=2021-03-09 |url-status=live |via=[[Flickr]] |lang=en}}
* {{Cite web |title=PDP-1 Music |url=http://www.dpbsmith.com/pdp1music/ |url-status=live |archive-url=https://web.archive.org/web/20211120014248/http://www.dpbsmith.com/pdp1music/ |archive-date=2021-11-20 |access-date=2022-03-23 |website=Daniel P. B. Smith |language=en}}
* {{Cite web |title=Spacewar! It Came from MIT |url=https://thedoteaters.com/?bitstory=bitstory-article-1/spacewar |url-status=live |archive-url=https://web.archive.org/web/20210418164735/https://thedoteaters.com/?bitstory=bitstory-article-1/spacewar |archive-date=2021-04-18 |access-date=2022-03-23 |website=The Dot Eaters: Video Game History 101 |language=en}}
* {{Cite web |title=Spacewar! - Original 1962 game code running on a PDP-1 emulator in JavaScript |url=http://spacewar.oversigma.com |url-status=live |archive-url=https://web.archive.org/web/20211125183543/https://spacewar.oversigma.com/ |archive-date=2021-11-25 |access-date=2022-03-23 |website=OverSigma |language=en}}
* {{Cite web |title=Welcome {{!}} PDP-1 Restoration Project |url=http://www.computerhistory.org/pdp-1/ |url-status=live |archive-url=https://web.archive.org/web/20220316020603/https://www.computerhistory.org/pdp-1/ |archive-date=2022-03-16 |access-date=2022-03-23 |website=[[Computer History Museum]] |language=en}}

{{DEC hardware}}

{{Authority control}}

{{DEFAULTSORT:Pdp-1}}
[[Category:DEC minicomputers]]
[[Category:Transistorized computers]]
[[Category:18-bit computers]]
[[Category:Computer-related introductions in 1959]]
[[Category:Computer-related introductions in 1960]]