Editing Dartmouth Time-Sharing System (section)

==Early history==
[[File:DTSS schematic.jpg|thumb|right|DTSS hardware schematic, October 1964]]
[[File:Ode to A Computer - GE-235 We Sing Thy Praises - Kiewit Supplement, The Dartmouth, December 2, 1966.jpg|thumb|right|GE-235 We Sing Thy Praises]]
Professors [[John George Kemeny|John Kemeny]] and [[Thomas E. Kurtz|Thomas Kurtz]] at Dartmouth College purchased a [[Royal McBee]] [[LGP-30]] computer around 1959, which was programmed by undergraduates in assembly language. Kurtz and four students programmed the [[Dartmouth ALGOL 30]] [[compiler]], an implementation of the [[ALGOL 58]] programming language, which two of the students, Stephen Garland and [[Anthony W. Knapp|Anthony Knapp]] then evolved into the SCALP (Self Contained ALgol Processor) language between 1962 and 1964. Kemeny and freshman Sidney Marshall collaborated to create [[DOPE (Dartmouth Oversimplified Programming Experiment)]], which was used in large freshman courses.<ref>''Application to the National Science Foundation'', Kurtz, Rieser, and Meck, cited in Rankin, pages 20-21</ref>

Kurtz approached Kemeny in either 1961 or 1962, with the following proposal:<ref>Rankin, pages 22-23</ref> all Dartmouth students would have access to computing, it should be free and open-access, and this could be accomplished by creating a time-sharing system (which Kurtz had learned about from colleague [[John McCarthy (computer scientist)|John McCarthy]] at [[MIT]], who suggested "why don't you guys do timesharing?"). Although it has been stated that DTSS was inspired by a [[PDP-1]]-based time-sharing system at [[BBN Technologies|Bolt, Beranek and Newman]], there is no evidence that this is true.{{fact|date=May 2024}}

In 1962, Kemeny and Kurtz submitted a proposal for the development of a new time-sharing system to [[National Science Foundation|NSF]] (which was ultimately funded in 1964).<ref name="computing-at-dartmouth-1960s" /> They had sufficient assurance that both Dartmouth and NSF would support the system that they signed a contract with [[GEISCO|GE]] and began preliminary work in 1963, before the proposal was funded.<ref>Rankin, pages 24-25</ref> In particular, they evaluated candidate computers from [[Bendix Corporation|Bendix]], [[General Electric|GE]], and [[IBM]], and settled upon the [[GE-225]] system paired with a [[DATANET-30]] communications processor. This two-processor approach was unorthodox, and Kemeny later recalled:<ref>''The GE-Dartmouth Computer Partnership'', John G. Kemeny, DTSS History Birth 1967-1970 Folder 2, Box 4, Garland Papers, Dartmouth College Library</ref> "At that time, many experts at GE and elsewhere, tried to convince us that the route of the two-computer solution was wasteful and inefficient." In essence, the DATANET-30 provided the user-interface and scheduler, while user programs ran in the GE-225.

Its implementation began in 1963, by a student team<ref>{{cite web |url=http://www.kemenyskids.com/ |title=Kemeny's Kids |url-status=usurped |archive-url=https://web.archive.org/web/20071009062028/http://www.kemenyskids.com/ |archive-date=2007-10-09}}</ref> under the direction of Kemeny and Kurtz with the aim of providing easy access to computing facilities for all members of the college.<ref>{{cite book |url=http://www.bitsavers.org/pdf/dartmouth/DTSS_descr_Oct64.pdf |title=The Dartmouth Time-Sharing System - A Brief Description |date=October 1964}}</ref> The GE-225 and DATANET-30 computers arrived in February 1964.  Two students, John McGeachie and Michael Busch, wrote the operating systems for the DATANET-30 and GE-225; Kemeny contributed the [[BASIC]] compiler.  The system became operational in mid March, and on May 1, 1964, at 4:00&nbsp;a.m., the system began operations.<ref>{{cite book |author=Gordon M. Bull |title=The Dartmouth Time-Sharing System |publisher=Ellis Horwood Ltd. and John Wiley & Sons |date=1980 |url=https://bitsavers.org/pdf/honeywell/large_systems/DTSS/The_Dartmouth_Time-Sharing_System_1980.pdf}} A description of DTSS c. 1977</ref> In autumn of 1964, hundreds of freshman students began to use the system via 20 [[Teleprinter|teletype]]s, with access at [[Hanover High School (New Hampshire)|Hanover High School]] via one additional teletype;<ref>Rankin, pages 33-34</ref> later that autumn the GE-225 computer was replaced with a faster [[GE-200 series|GE-235]] computer with minimal issues. By summer of 1965, the system could support forty simultaneous users.<ref>Bull, page 13</ref>

A Dartmouth document from October 1964, later revised by GE, describes the overall DTSS architecture:<ref>"The Dartmouth Time-Sharing System, A Brief Description", October 19, 1964, with revisions by GE staff, 1965</ref> 
<blockquote>The program in the Datanet-30 is divided into two parts, a real-time part and a spare-time part. The real-time part is entered via clock-controlled [[interrupt]] 110 times per second in order to scan the teletype lines. As characters are completed, the real-time part collects them into messages and, when a "return" character is encountered, interprets the message. If it is a line in the program, nothing is done. If the message is a command, a spare-time task to start carrying out the command is set up and inserted in the spare-time list. If there is not enough time to complete this setting-up, the real-time part will complete the set-up during the next real-time period. The spare-time portion carries out the spare-time tasks, which include mainly disc operations and certain teletype operations. In the GE-235 part there is resident compiler system that acts as a translator, and a resident executive routine to manage the disc input-output operations and to perform other functions. The executive system permits simultaneous use of the card equipment, the tape drives, and the high-speed printer during time-sharing through interrupt processing. Two [[algebra]]ic languages, BASIC and ALGOL, are available, with FORTRAN planned for September 1965. These one-pass compilers are rather fast, requiring usually 1 to 4 seconds per compilation.</blockquote>