Digital encoding of APL symbols: Difference between revisions

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==Character sets==

Due to its origins on [[IBM]] [[IBM Selectric typewriter|Selectric]]-based [[teleprinter]]s, APL symbols have traditionally been represented on the wire{{jargon inline|date=August 2025}} using a unique, non-standard character set. In the 1960s and 1970s, few terminal devices existed which could reproduce them, the most popular ones being the [[IBM 2741]] and [[IBM 1050]] fitted with a specific APL print head. Over time, with the universal use of high-quality graphic display, printing devices and [[Unicode]] support, the APL character font problem has largely been eliminated.

===Character repertoire===

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|SL210000 || Up Shoe Null (APL) || {{unichar|235D|APL FUNCTIONAL SYMBOL UP SHOE JOT}} ||

|-

|SL220000 || Up Tack (APL){{efn |name=tacks}} || {{unichar|22A4|DOWN TACK}}{{efn|There are two naming conventions (which way around "up" and "down" are, and which way around "left" and "right" are) for tack characters, the "London" and "Bosworth" conventions.<ref name="dickey">{{cite web |url=https://www.math.uwaterloo.ca/~ljdickey/apl-rep/tables/note1.html |last=Dickey |first=Leroy J. |title=The Naming of Tack Symbols |website=University of Waterloo}}</ref> Which convention is used differs between IBM and Unicode. Naming also differs between composite Unicode characters intended solely for APL (which match IBM naming and use the Bosworth convention) versus plain tacks also intended for other applications (which use the London convention).<ref name="dickey"/><ref name="utn27">{{cite web |url=https://www.unicode.org/notes/tn27/ |title=Known Anomalies in Unicode Character Names |date=2021-06-14 |first1=Asmus |last1=Freytag |first2=Rick |last2=McGowan |first3=Ken |last3=Whistler |publisher=[[Unicode Consortium]] |id=UTN #27}}</ref> APL specifications subsequently adopted the London convention.<ref name="utn27"/> The documentation for Dyalog APL notes that the Unicode naming for composite tacks (and thus the IBM naming for all tacks), which follows the the lesser-used "Bosworth" convention,<ref name="dickey"/> runs contrary to convention in the APL community.{{refn|name=dyalogsheet}} |name=tacks}} ||

|-

|SL230000 || Down Tack (APL){{efn |name=tacks}} || {{unichar|22A5|UP TACK}}{{efn |name=tacks}} ||

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|SL300000 || Equal Underbar (APL) || {{unichar|2261|IDENTICAL TO}} ||

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|SL310000 || OUT Symbol (APL)<ref name="slgcgidchart"/> || none{{efn|Unicode 1.0 had the "APL out" character at U+2301, but it was removed in Unicode 1.0.1.<ref>{{cite web|url=https://www.unicode.org/versions/Unicode1.0.0/Notice.pdf|title=Unicode 1.0.1 Addendum|work=The Unicode Standard|date=1992-11-03|accessdate=2024-09-21}}</ref>}} || Not used in any IBM-documented code page. ReferenceIBM's reference glyph resembles oblique underlined forms of the letters O, U and T overstruck in the same character position.

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|SL320000 || Diaeresis Dot (APL) || {{unichar|2235|BECAUSE}} ||

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|{{chset-ctrl1||&nbsp;{{control code link|EO}}&nbsp;}}

|}

{{legend|#FFD|Differences from [[Code page 37]]}}

====Code page 310====

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====Code page 907====

'''Code page 907''' is used by the IBM 3812, like [[code page 906]].

{|{{chset-table-header1|Code page 907<ref name="cpgid907">{{citation|mode=cs1 |archive-url=https://web.archive.org/web/20170803005351/http://www-03.ibm.com/systems/resources/systems_i_software_globalization_pdf_cp00907z.pdf |archive-date=2017-08-03 |url=http://www-03.ibm.com/systems/resources/systems_i_software_globalization_pdf_cp00907z.pdf |title=Code Page 00907 |author=IBM |author-link=IBM}}</ref>}}

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==Keyboard layout==

NoteThere theare mnemonics associating an APL character with a letter: {{keypress|?}} (''question mark'') on {{keypress|Q}}, {{keypress|⋆}} (''power'') on {{keypress|P}}, {{keypress|ρ}} (''rho'') on {{keypress|R}}, {{keypress|⊥}} (''base value'') on {{keypress|B}}, {{keypress|⊤}} (''eNcode'') on {{keypress|N}}, {{keypress|∣}} (''modulus'') on {{keypress|M}} and so on. This makes it easier for an English-language speaker to type APL on a non-APL keyboard, providing one has visual feedback on one's screen. Also, decals have been produced for attachment to standard keyboards, either on the front of the keys or on the top of them.

[[Image:APL-keybd2.svg|600px|thumb|center|APL keyboard layout.<ref>

A more up-to-date keyboard diagram, applicable for APL2 and other modern implementations, is available at WikensOnline '''[http://www.wickensonline.co.uk/apl/union-large.png Union APL large keyboard layout for Windows] {{webarchive |url=https://web.archive.org/web/20120310113525/http://www.wickensonline.co.uk/apl/union-large.png |date=March 10, 2012 }}''', '''[http://www.wickensonline.co.uk/apl-unicomp.html actual photo + diagram here] {{webarchive |url=https://web.archive.org/web/20150403042056/http://www.wickensonline.co.uk/apl-unicomp.html |date=April 3, 2015 }}''' and '''[http://www.sudleyplace.com/APL/Keyboard.ahtml NARS2000 APL keyboard layout here]'''.</ref>]]

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==External links==

*[http://www-01.ibm.com/software/globalization/cp/cp00293.html IBM code page 293] a.k.a. the APL code page on [[mainframe computer]]s

*[https://web.archive.org/web/20110605162417/http://www-03.ibm.com/systems/resources/systems_i_software_globalization_pdf_cp00907z.pdf IBM code page 907] a.k.a. the APL ASCII code page

{{Character encoding}}