Code pages used specifically to write programs in the APL programming language
The programming language APL uses a number of symbols, rather than words from natural language, to identify operations, similarly to mathematical symbols. Prior to the wide adoption of Unicode, a number of special-purpose EBCDIC and non-EBCDIC code pages were used to represent the symbols required for writing APL.
Due to its origins on IBMSelectric-based teleprinters, APL symbols have traditionally been represented on the wire 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
IBM assigns the following character IDs (GCGIDs) to APL syntax, which are used in the definitions of its code pages.[1][2][3]
This is SM750000 in a non-APL context, for example, in the C0 replacement graphics from code page 437,[8] which code pages 907, 909 and 910 inherit some or all of, retaining SM750000 in the C0 area and also including SL080000 outside of it.[9][10][11] Both map to U+25CB when APL is represented using Unicode characters, although SL080000 can be mapped to U+F890 in IBM's private use area scheme.[12] Compare SL590000 through SL620000 below.
Not used in any documented code page. Reference glyph resembles oblique underlined forms of the letters O, U and T overstruck in the same character position.
U+F88F in IBM's private use area scheme.[12] Also mapped to U+007E~TILDE,[15][6][7] although SD190000 (U+007E in a non-APL context) co-occurs at 0xA1 (while SL460000 is at 0x80) in code page 213.[16]
U+F88E in IBM's private use area scheme.[12] SP020000 (U+0021!EXCLAMATION MARK in a non-APL context) co-occurs at 0x5A in code page 293 (SL580000 is at 0xDB in code pages 293 and 310).[16] Tachyonsoft lists U+01C3ǃLATIN LETTER RETROFLEX CLICK for SL580000.[4]
These arrows are SM300000, SM310000, SM320000 and SM330000 respectively in a non-APL context, for example, in the C0 replacement graphics from code page 437,[8] which code pages 907, 909 and 910 inherit some or all of. Their APL GCGIDs can be mapped to U+F88D, U+F88C, U+F88B and U+F88A respectively in IBM's private use area scheme.[12]
Code pages 907 and 910 keep the non-APL GCGIDs for the C0 replacements but use the APL GCGIDs where the arrows appear outside of the C0 area, while code page 909 uses the APL GCGIDs multiple times, both for the C0 replacements and for between one and two occurrences of each of these arrows outside of the C0 area.[9][10][11]
Compare SL080000 above. Duplicating C0 replacement graphics outside of the C0 area is not an uncommon practice in DOS code pages: compare, for example, the pilcrow and section sign in code page 850.
U+F889 in IBM's private use area scheme.[12] Also mapped to U+2216∖SET MINUS.[4] SM070000 (U+005C\REVERSE SOLIDUS in a non-APL context) co-occurs at 0x5A (while SL640000 is at 0xB7) in code page 293.[16]
Form with fullwidth attribute set (SL830080) is used for 0xA1C3 (i.e. U+2236∶RATIO) in EUC-CN.[18]
SL840000
Dot (APL)
U+002E.FULL STOP
SL850000
Comma (APL)
U+002C,COMMA
SL860000
Iota Underbar (APL)
U+2378⍸APL FUNCTIONAL SYMBOL IOTA UNDERBAR
SL870000
Epsilon Underbar (APL)
U+2377⍷APL FUNCTIONAL SYMBOL EPSILON UNDERBAR
EBCDIC code pages
Code page 293
Code page 293 (CCSID 293),[19] called "APL (USA)", is an EBCDIC code page which includes APL symbols, in addition to preserving the basic Latin letters and Western Arabic numerals at their usual EBCDIC locations.[16][17]
Code page 310 ("Graphic Escape APL/TN") includes a larger gamut of symbols, but does not itself include the basic Latin letters or the basic digits.[21][4] It is used alongside Code page 37-2,[22] with the Code page 310 codes being prefixed by the Graphic Escape (EBCDIC 0x08)[23] control character.[6][24]
Code page 351 ("GDDM Default (USA)")[26] contains most of the characters of Code page 293 and Code page 310 (except ⍷, epsilon with underline) in addition to the letters and digits, by replacing several control characters with symbols.
Code page 371,[27] registered for use with ISO/IEC 2022 as ISO-IR-68,[28][5] is a 7-bit heavily modified ASCII, designed by the APL Working Group of the Canadian Standards Association, intended for use with APL in an environment allowing overstriking of characters using the BS (backspace, 0x08) control code.[28][5]
8-bit modified and/or extended ASCII
Code page 907
Code page 907 is used by the IBM 3812, like code page 906.
Code page 909 is another encoding for APL, differing from code page 907 in not including the underlined characters, assigning different codes to the APL characters which fall in the 0xB0–DF range, and replacing some of the C0 replacement graphics from code page 437 with alternative encodings for certain APL symbols.
Code page 910 is similar to code page 909, but with fewer duplicate horizontal arrows, using the same C0 graphics as code page 437, and including some additional characters.
Most APL symbols are present in Unicode, in the Miscellaneous Technical range,[29] although some APL products may not yet feature Unicode, and some APL symbols may be unused or unavailable in a given vendor's implementation.
As of 2010, Unicode allows APL to be stored in text files, published in print and on the web, and shared through email and instant messaging. Entering APL characters still requires the use of either a specific input method editor or keyboard mapping, or of a specific touch interface. APL keyboard mappings are available for free for the most common operating systems, or can be obtained by adding the Unicode APL symbols to existing keyboard map.
Underscored alphabetic characters
Missing from Unicode are the traditional underscored alphabetic characters included in some of the APL code pages; their usage has been eliminated or deprecated in most APL implementations. These were produced on APL printing terminals by over-striking a straight capital letter with an underscore character. Some tables show them simulated with underlined and italic markup, not listing Unicode mappings.[4]
IBM assigns them GCGIDs as "LA480000" (which they name "A Line Below Capital/A Underscore (APL)"), "LB480000" ("B Line Below Capital/B Underscore (APL)") and so forth, under the "L" series used for Latin letters.[1] The use of an even number (48) rather than an odd number (47) is due to being uppercase: compare the use of SD110000 for a lone acute accent ´, LA110000 for the lowercase á, and LA120000 for the uppercase Á.[30] They are included in IBM's private use area scheme, encoded in reverse‑alphabetical order in the odd-numbered code points from U+F8BF to U+F8F1.[12]
Homologous uses of 47 include the "SD" (diacritic) series GCGID SD470000 for "Line Below/Discontinuous Underscore"[31]—i.e. macron below, distinct from the ASCII underscore which is SP090000 ("Underline/Continuous Underscore")[30]—and the "A" (Arabic letter) series GCGID AD470009 for the ḏāl,[32] for example. Unicode's Latin Extended Additional block includes the following capital "Line Below" characters with the macron below diacritic, for Semitic transcription (it includes a pre-composed ẖ only in lowercase):
U+1E06ḆLATIN CAPITAL LETTER B WITH LINE BELOW
U+1E0EḎLATIN CAPITAL LETTER D WITH LINE BELOW
U+1E34ḴLATIN CAPITAL LETTER K WITH LINE BELOW
U+1E3AḺLATIN CAPITAL LETTER L WITH LINE BELOW
U+1E48ṈLATIN CAPITAL LETTER N WITH LINE BELOW
U+1E5EṞLATIN CAPITAL LETTER R WITH LINE BELOW
U+1E6EṮLATIN CAPITAL LETTER T WITH LINE BELOW
U+1E94ẔLATIN CAPITAL LETTER Z WITH LINE BELOW
However, this does not cover the entire ISO basic Latin alphabet, and IBM's reference glyphs for the APL characters show them both underlined and oblique,[2] and tables simulating them with markup may follow suit.[4] Unicode's Mathematical Alphanumeric Symbols block includes italic characters for use in notations where they are contrastive with non-italic characters. Unicode also includes combining forms of the macron below and underscore in the Combining Diacritical Marks block; the characters above canonically decompose with the former:
U+0331◌̱COMBINING MACRON BELOW
U+0332◌̲COMBINING LOW LINE
Keyboard layout
Note the mnemonics associating an APL character with a letter: ? (question mark) on Q, ⋆ (power) on P, ρ (rho) on R, ⊥ (base value) on B, ⊤ (eNcode) on N, ∣ (modulus) on 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.
APL keyboard layout.
Later IBM terminals, notably the IBM 3270 display stations, had an alternate keyboard arrangement which is the basis for some of the modern APL keyboard layouts in use today.
Further APL characters were available by overstriking one character with another. For example, the log symbol (⍟) was formed by overstriking ⇧ Shift+P with ⇧ Shift+O. This extended the graphic abilities of the earlier teleprinters, but made it more complex to correct errors and edit program lines.
New overstrikes were introduced by vendors as they produced versions of APL tailored to specific hardware, system features, file systems, and so on. Further, printing terminals and early APL cathode-ray terminals were able to display arbitrary overstrikes, but as personal computers rapidly replaced terminals as a data-entry device, APL character support became provided as an APL Character Generator ROM or a soft character set rendered by the display device. With the advent of the modern PC, APL characters were defined in specific fonts, eliminating the distinction between overstruck characters and standard characters.
Finally, the symbols were ratified in Unicode and given specific code points, with unambiguous interpretations, independently of the graphic font.
1 2 3 4 5 6 7 8 9 10 11 12 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.[13] 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).[13][14] APL specifications subsequently adopted the London convention.[14] The documentation for Dyalog APL notes that the Unicode naming for composite tacks (and thus the IBM naming for all tacks), which follows the lesser-used "Bosworth" convention,[13] runs contrary to convention in the APL community.[7]
Extended Binary Coded Decimal Interchange Code is an eight-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems. It descended from the code used with punched cards and the corresponding six-bit binary-coded decimal code used with most of IBM's computer peripherals of the late 1950s and early 1960s. It is supported by various non-IBM platforms, such as Fujitsu-Siemens' BS2000/OSD, OS-IV, MSP, and MSP-EX, the SDS Sigma series, Unisys VS/9, Unisys MCP and ICL VME.
ISO/IEC 8859-1:1998, Information technology — 8-bit single-byte coded graphic character sets — Part 1: Latin alphabet No. 1, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. ISO/IEC 8859-1 encodes what it refers to as "Latin alphabet no. 1", consisting of 191 characters from the Latin script. This character-encoding scheme is used throughout the Americas, Western Europe, Oceania, and much of Africa. It is the basis for some popular 8-bit character sets and the first two blocks of characters in Unicode.
ISO/IEC 8859-3:1999, Information technology — 8-bit single-byte coded graphic character sets — Part 3: Latin alphabet No. 3, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1988. It is informally referred to as Latin-3 or South European. It was designed to cover Turkish, Maltese and Esperanto, though the introduction of ISO/IEC 8859-9 superseded it for Turkish. The encoding was popular for users of Esperanto, but fell out of use as application support for Unicode became more common.
ISO/IEC 646 is a set of ISO/IEC standards, described as Information technology — ISO 7-bit coded character set for information interchange and developed in cooperation with ASCII at least since 1964. Since its first edition in 1967 it has specified a 7-bit character code from which several national standards are derived.
In computing, a code page is a character encoding and as such it is a specific association of a set of printable characters and control characters with unique numbers. Typically each number represents the binary value in a single byte.
The yen and yuan sign (¥) is a currency sign used for the Japanese yen and the Chinese yuan currencies when writing in Latin scripts. This character resembles a capital letter Y with a single or double horizontal stroke. The symbol is usually placed before the value it represents, for example: ¥50, or JP¥50 and CN¥50 when disambiguation is needed. When writing in Japanese and Chinese, the Japanese kanji and Chinese character is written following the amount, for example ５０円 in Japan, and ５０元 or ５０圆 in China.
ISO/IEC 8859-11:2001, Information technology — 8-bit single-byte coded graphic character sets — Part 11: Latin/Thai alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 2001. It is informally referred to as Latin/Thai. It is nearly identical to the national Thai standard TIS-620 (1990). The sole difference is that ISO/IEC 8859-11 allocates non-breaking space to code 0xA0, while TIS-620 leaves it undefined.
ISO/IEC 8859-8, Information technology — 8-bit single-byte coded graphic character sets — Part 8: Latin/Hebrew alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings. ISO/IEC 8859-8:1999 from 1999 represents its second and current revision, preceded by the first edition ISO/IEC 8859-8:1988 in 1988. It is informally referred to as Latin/Hebrew. ISO/IEC 8859-8 covers all the Hebrew letters, but no Hebrew vowel signs. IBM assigned code page 916 to it. This character set was also adopted by Israeli Standard SI1311:2002, with some extensions.
ISO/IEC 8859-4:1998, Information technology — 8-bit single-byte coded graphic character sets — Part 4: Latin alphabet No. 4, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1988. It is informally referred to as Latin-4 or North European. It was designed to cover Estonian, Latvian, Lithuanian, Greenlandic, and Sámi. It has been largely superseded by ISO/IEC 8859-10 and Unicode. Microsoft has assigned code page 28594 a.k.a. Windows-28594 to ISO-8859-4 in Windows. IBM has assigned code page 914 to ISO 8859-4.
ISO/IEC 8859-7:2003, Information technology — 8-bit single-byte coded graphic character sets — Part 7: Latin/Greek alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. It is informally referred to as Latin/Greek. It was designed to cover the modern Greek language. The original 1987 version of the standard had the same character assignments as the Greek national standard ELOT 928, published in 1986. The table in this article shows the updated 2003 version which adds three characters. Microsoft has assigned code page 28597 a.k.a. Windows-28597 to ISO-8859-7 in Windows. IBM has assigned code page 813 to ISO 8859-7. (IBM CCSID 813 is the original encoding. CCSID 4909 adds the euro sign. CCSID 9005 further adds the drachma sign and ypogegrammeni.)
ISO/IEC 8859-9:1999, Information technology — 8-bit single-byte coded graphic character sets — Part 9: Latin alphabet No. 5, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1989. It is designated ECMA-128 by Ecma International and TS 5881 as a Turkish standard. It is informally referred to as Latin-5 or Turkish. It was designed to cover the Turkish language, designed as being of more use than the ISO/IEC 8859-3 encoding. It is identical to ISO/IEC 8859-1 except for the replacement of six Icelandic characters with characters unique to the Turkish alphabet. And the uppercase of i is İ; the lowercase of I is ı.
Code page 850 is a code page used under DOS and Psion's EPOC16 operating systems in Western Europe. Depending on the country setting and system configuration, code page 850 is the primary code page and default OEM code page in many countries, including various English-speaking locales, whilst other English-speaking locales default to use the hardware code page 437.
Code page 437 is the character set of the original IBM PC. It is also known as CP437, OEM-US, OEM 437, PC-8, or DOS Latin US. The set includes all printable ASCII characters as well as some accented letters (diacritics), Greek letters, icons, and line-drawing symbols. It is sometimes referred to as the "OEM font" or "high ASCII", or as "extended ASCII".
Several 8-bit character sets (encodings) were designed for binary representation of common Western European languages, which use the Latin alphabet, a few additional letters and ones with precomposed diacritics, some punctuation, and various symbols. These character sets also happen to support many other languages such as Malay, Swahili, and Classical Latin.
In Unicode, a Private Use Area (PUA) is a range of code points that, by definition, will not be assigned characters by the Unicode Consortium. Three private use areas are defined: one in the Basic Multilingual Plane, and one each in, and nearly covering, planes 15 and 16. The code points in these areas cannot be considered as standardized characters in Unicode itself. They are intentionally left undefined so that third parties may define their own characters without conflicting with Unicode Consortium assignments. Under the Unicode Stability Policy, the Private Use Areas will remain allocated for that purpose in all future Unicode versions.
The C0 and C1 control code or control character sets define control codes for use in text by computer systems that use ASCII and derivatives of ASCII. The codes represent additional information about the text, such as the position of a cursor, an instruction to start a new line, or a message that the text has been received.
Windows code pages are sets of characters or code pages used in Microsoft Windows from the 1980s and 1990s. Windows code pages were gradually superseded when Unicode was implemented in Windows, although they are still supported both within Windows and other platforms, and still apply when Alt code shortcuts are used.
The programming language APL is distinctive in being symbolic rather than lexical: its primitives are denoted by symbols, not words. These symbols were originally devised as a mathematical notation to describe algorithms. APL programmers often assign informal names when discussing functions and operators but the core functions and operators provided by the language are denoted by non-textual symbols.
IBM code page 949 (IBM-949) is a character encoding which has been used by IBM to represent Korean language text on computers. It is a variable-width encoding which represents the characters from the Wansung code defined by the South Korean standard KS X 1001 in a format compatible with EUC-KR, but adds IBM extensions for additional hanja, additional precomposed Hangul syllables, and user-defined characters.
Several mutually incompatible versions of the Extended Binary Coded Decimal Interchange Code (EBCDIC) have been used to represent the Japanese language on computers, including variants defined by Hitachi, Fujitsu, IBM and others. Some are variable-width encodings, employing locking shift codes to switch between single-byte and double-byte modes. Unlike other EBCDIC locales, the lowercase basic Latin letters are often not preserved in their usual locations.
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