Editing Backslash (section)

==History==
<!-- The copyright on Teletype Corporation documents cited in this section (and held in an independent third party repository) has expired. -->
[[File:Teletype Wheatstone Perforator keyboard.jpg|thumb|A Teletype Wheatstone Perforator keyboard from the 1930s, with backslash in the end of the third row]]
[[File:Mappa Teletype ASR-33.jpg|thumb|Teletype ASR-33 keyboard layout with ASCII character set, prior to June 14, 1966, with backslash on shift+L]]
{{as of|2022|11}}, efforts to identify either the origin of this character or its purpose before the 1960s have not been successful. The earliest known reference found to date is a 1937 maintenance manual from the [[Teletype Corporation]] with a photograph showing the keyboard of its [[Kleinschmidt keyboard perforator]] WPE-3 using the [[Wheatstone system]].<ref>{{citation |mode=cs1 |title=Bulletin 125, issue 2: Description and Adjustments of the Teletype Wheatstone Perforator |publisher=Teletype Corporation |date=May 1938 |orig-date=August 1937 |url=http://www.navy-radio.com/manuals/tty/tty125.pdf |page=ii |via=navy-radio.com |access-date=2021-03-15 |archive-date=2021-02-12 |archive-url=https://web.archive.org/web/20210212121807/http://www.navy-radio.com/manuals/tty/tty125.pdf |url-status=live }}</ref><ref name=Fischer /> The symbol was called the "diagonal key",<ref>{{cite web |title=Bulletin 188: Teletype automatic perforator set |page=6 |url=https://www.navy-radio.com/manuals/tty/188B-4508.pdf |publisher=Teletype Corporation |date=August 1945 |via=navy-radio.com |access-date=2021-12-19 |archive-date=2021-12-19 |archive-url=https://web.archive.org/web/20211219004736/https://www.navy-radio.com/manuals/tty/188B-4508.pdf |url-status=live}}</ref> and given a (non-standard) [[Morse code]] of {{morse|dot|dash|dot|dot|dash}}.<ref>{{cite web |title=Bulletin 1025, issue 3: Parts for Teletype Wheatstone Perforator |page=9 |url=https://www.navy-radio.com/manuals/tty/tty1025.pdf |date=July 1945 |publisher=Teletype Corporation |via=navy-radio.com |access-date=2021-12-19 |archive-date=2021-12-19 |archive-url=https://web.archive.org/web/20211219003141/https://www.navy-radio.com/manuals/tty/tty1025.pdf |url-status=live }}</ref>{{efn|This is the inverse of the code for the slash symbol ({{morse|dash|dot|dot|dash|dot}}).}}

In June 1960, [[IBM]] published an "Extended character set standard" that includes the symbol at 0x19.<ref name=Fischer>{{cite web |title=The Evolution of Character Codes, 1874–1968 |date=20 June 2000 |first=Eric |last=Fischer |pages=14–15 (Table 35) |url=http://dump.deadcodersociety.org/ascii.pdf |access-date=30 November 2022 |archive-date=30 November 2022 |archive-url=https://web.archive.org/web/20221130065133/http://dump.deadcodersociety.org/ascii.pdf |url-status=live }} Referencing {{cite tech report |first1=R.W. |last1=Bemer |first2=W. |last2=Buchholz |title=An Extended Character Set Standard |id=TR 00.721  |publisher=Product Development Laboratory, Data Systems Division, International Business Machines Corporation |date=June 1, 1960}} Computer Standards Collection, Archives Center, National Museum of American History, Smithsonian Institution, box 1.</ref> In September 1961, [[Bob Bemer]] (IBM) proposed to the [[International Committee for Information Technology Standards|X3.2 standards committee]] that {{code|[}}, {{code|]}} and {{code|\}} be made part of the proposed standard, describing the backslash as a "reverse division operator" and cited its prior use by Teletype in telecommunications. In particular, he said, the {{mono|\}} was needed so that the [[ALGOL 68#Standard dyadic operators with associated priorities|ALGOL Boolean operators]] {{code|∧}} ([[logical conjunction]]) and {{code|∨}} ([[logical disjunction]]) could be composed using {{mono|/\}} and {{mono|\/}} respectively. The Committee adopted these changes into the draft American Standard (subsequently called [[ASCII]]) at its November 1961 meeting.<ref name=Fischer />

These operators were used for min and max in early versions of the [[C (programming language)|C programming language]] supplied with Unix V6<ref>{{cite web |url=http://www.bitsavers.org/bits/Interdata/32bit/unix/univWollongong%5Fv6/interdata%5Fv6/usr/source/c/c00.c |title=C compiler source |date=1975 |website=bitsavers.org |access-date=2009-10-11 |archive-date=2011-08-15 |archive-url=https://web.archive.org/web/20110815153104/http://www.bitsavers.org/bits/Interdata/32bit/unix/univWollongong_v6/interdata_v6/usr/source/c/c00.c |url-status=live }}</ref> and V7.<ref>{{cite web |url=http://stuff.mit.edu/afs/sipb/project/v7unix/fs/usr/src/cmd/c/c00.c |title=C compiler source |date=1979 |website=mit.edu |access-date=2009-10-11 |archive-date=2013-12-03 |archive-url=https://web.archive.org/web/20131203022053/http://stuff.mit.edu/afs/sipb/project/v7unix/fs/usr/src/cmd/c/c00.c |url-status=live }}</ref>