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DEC NRCS encoding family

Invariant subset of NRCS. Red Bowen knots (⌘) denote national code points.
Alias(es)	National Replacement Character Set
Preceded by	ASCII
Succeeded by	ISO 8859, ISO 10646
Other related encoding(s)	ISO 646
v t e

The National Replacement Character Set (NRCS) was a feature supported by later models of Digital's (DEC) computer terminal systems, starting with the VT200 series in 1983. NRCS allowed individual characters from one character set to be replaced by one from another set, allowing the construction of different character sets on the fly. It was used to customize the character set to different local languages, without having to change the terminal's ROM for different countries, or alternately, include many different sets in a larger ROM. Many 3rd party terminals and terminal emulators supporting VT200 codes also supported NRCS.

Description

ASCII is a 7-bit standard, allowing a total of 128 characters in the character set. Some of these are reserved as control characters, leaving 96 printable characters. This set of 96 printable characters includes upper and lower case letters, numbers, and basic math and punctuation.

ASCII does not have enough room to include other common characters such as multi-national currency symbols or the various accented letters common in European languages. This led to a number of country-specific varieties of 7-bit ASCII with certain characters replaced. For instance, the UK standard simply replaced ASCII's hash mark, #, with the pound symbol, £. This normally led to different models of a given computer terminal or printer, differing only in the glyphs stored in ROM. Some of these were standardized as part of ISO/IEC 646.

On an 8-bit clean serial link, ASCII can be expanded to support a total of 256 characters. In this case, instead of replacing the characters in the original printable characters range from 32 to 127, new characters are added in the 128 to 255 range. This offers enough room for a single character set to include all the variety of characters used in North America and western Europe. This capability led to the introduction of the ISO/IEC 8859-1 standard character set containing 191 characters of what it calls the "Latin alphabet no. 1", but normally referred to as "ISO Latin". Windows-1252 is a slightly expanded superset of ISO Latin.

NRCS was introduced to solve the problem of requiring different terminals for each country by allowing characters in the basic 7-bit ASCII set to be re-defined by copying the glyph from the DEC's version of ISO Latin, the Multinational Character Set (MCS). This meant that the ROM had to store only two character sets, standard ASCII and MCS, and could build any required local ASCII variant on the fly. For instance, instead of having a separate "UK ASCII" version of the terminal with a modified glyph in ROM, the terminal included an NRCS with instructions to replace the hash mark glyph with the pound. When used in the UK, typing Shift 3 produced the pound, the same keys pressed on a US terminal produced hash.

The NRCS could be set through a setup command, or more commonly, by replacing the keyboard with a model that sent back a code when first booted. That way simply plugging in a UK keyboard, which had a pound sign on the 3 key, automatically set the NRCS to that same replacement.

NRC Sets

DEC terminals from the VT220 on had 12 different NRCS sets in addition to standard ASCII:

See also

• 7-bit DEC Greek
• 7-bit DEC Hebrew (SI 960, HEBREW-7)
• 7-bit DEC Turkish (TR7DEC)
• 7-bit DEC Cyrillic (KOI-7)

Notes

1. ^ This DEC character set is similar to ISO 646-PT2 / IR 84 aka IBM code page 1015, except for code point 64 (0x40), which is assigned to "@" in the DEC character set, but to "´" in the ISO character set.

References

1. Hartman Kennelly, Cynthia (1991). Unch, Jacqueline (ed.). Digital Guide To Developing International Software (1 ed.). Digital Equipment Corporation. ISBN 1-55558-063-7. EY-F577E-DP.
2. ^ DEC (June 1987). "Appendix E". VT320 Programming Summary. Digital Press. (The provided link goes to a digitized version, which contains some subtle OCR errors, therefore isn't a reliable reference for the character set mappings)
3. ^ DEC (February 1992) . "Chapter 2: Character Encoding - National Replacement Character Sets (NRC Sets) (Worldwide Models Only)". VT420 Programmer Reference Manual (PDF) (2 ed.). Digital Equipment Corporation. p. 28. EK–VT420–RM.002. Archived (PDF) from the original on 2017-01-29. Retrieved 2017-01-29.
4. ^ "VT220 Programmer Reference Manual" (2 ed.). Digital Equipment Corporation (DEC). 1984 .
5. "SBCS code page information - CPGID: 01101 / Name: British NRC Set". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.
6. ^ Digital Equipment Corporation (DEC). "7. Character Sets". VT510 Video Terminal Programmer Information. Retrieved 2017-02-18.
7. "SBCS code page information - CPGID: 01107 / Name: Norwegian/Danish NRC Alternate". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.
8. "SBCS code page information - CPGID: 01105 / Name: Norwegian/Danish NRC Set". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.
9. ^ "SBCS code page information - CPGID: 01102 / Name: Dutch NRC Set". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.
10. "SBCS code page information - CPGID: 01103 / Name: Finnish NRC Set". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.
11. ^ "SBCS code page information - CPGID: 01104 / Name: French NRC Set". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.
12. "SBCS code page information - CPGID: 01020 / Name: Canadian (French) Variant". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.
13. "SBCS code page information - CPGID: 01011 / Name: 7-Bit Germany F.R." IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1987-08-01. Archived from the original on 2016-06-17. Retrieved 2016-06-17.
14. "Code Page Identifiers". Microsoft Developer Network. Microsoft. 2014. Archived from the original on 2016-06-19. Retrieved 2016-06-19.
15. "Web Encodings - Internet Explorer - Encodings". WHATWG Wiki. 2012-10-23. Archived from the original on 2016-06-20. Retrieved 2016-06-20.
16. Foller, Antonin (2014) . "German (IA5) encoding - Windows charsets". WUtils.com - Online web utility and help. Motobit Software. Archived from the original on 2016-06-20. Retrieved 2016-06-20.
17. ^ Bemer, Robert William (1980). "Chapter 1: Inside ASCII". General Purpose Software (PDF). Best of Interface Age. Vol. 2. Portland, OR, USA: dilithium Press. pp. 1–50. ISBN 0-918398-37-1. LCCN 79-67462. Archived from the original on 2016-08-27. Retrieved 2016-08-27, from: Bemer, Robert William (May 1978). "Inside ASCII - Part I". Interface Age. 3 (5). Portland, OR, USA: dilithium Press: 96–102., Bemer, Robert William (June 1978). "Inside ASCII - Part II". Interface Age. 3 (6). Portland, OR, USA: dilithium Press: 64–74., Bemer, Robert William (July 1978). "Inside ASCII - Part III". Interface Age. 3 (7). Portland, OR, USA: dilithium Press: 80–87.
18. ^ "HP PCL/PJL Reference PCL 5 Comparison Guide" (PDF) (2 ed.). Hewlett-Packard Company, LP. June 2003. HP part-number 502-0378. Archived from the original (PDF) on 2016-08-10. Retrieved 2016-08-10.
19. ^ "SBCS code page information - CPGID: 01012 / Name: 7-Bit Italy". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1987-08-01. Archived from the original on 2016-06-17. Retrieved 2016-06-17.
20. ^ "SBCS code page information - CPGID: 01023 / Name: Spain Variant". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.
21. "SBCS code page information - CPGID: 01106 / Name: Swedish British NRC Set". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.
22. "SBCS code page information - CPGID: 01021 / Name: Switzerland Variant". IBM Software: Globalization: Coded character sets and related resources: Code pages by CPGID: Code page identifiers. 1. IBM. 1992-10-01. Archived from the original on 2016-12-05. Retrieved 2016-12-05.

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Character sets	Code page 1100 (Multinational) Code page 1287 (Greek) Code page 1288 (Turkish) Hebrew National Replacement RADIX 50 Special Graphics Technical
Bus standards	Digital Storage Systems Interconnect Massbus Q-Bus Standard Disk Interconnect Synchronous Backplane Interconnect TURBOchannel Unibus VAXBI bus
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v t e Character encodings
Early telecommunications	Telegraph code Needle Morse Non-Latin Wabun/Kana Chinese Cyrillic Baudot and Murray Fieldata ASCII ISO/IEC 646 BCDIC Teletex and Videotex/Teletext T.51/ISO/IEC 6937 ITU T.61 ITU T.101 World System Teletext background sets Transcode
ISO/IEC 8859	Approved parts -1 (Western Europe) -2 (Central Europe) -3 (Maltese/Esperanto) -4 (North Europe) -5 (Cyrillic) -6 (Arabic) -7 (Greek) -8 (Hebrew) -9 (Turkish) -10 (Nordic) -11 (Thai) -13 (Baltic) -14 (Celtic) -15 (New Western Europe) -16 (Romanian) Abandoned parts -12 (Devanagari) Proposed but not approved KOI-8 Cyrillic Sámi Adaptations Welsh Barents Cyrillic Estonian Ukrainian Cyrillic
Bibliographic use	MARC-8 ANSEL CCCII/EACC ISO 5426 5426-2 5427 5428 6438 6862
National standards	ArmSCII Big5 BraSCII CNS 11643 DIN 66003 ELOT 927 GOST 10859 GB 2312 GB 12345 GB 12052 GB 18030 HKSCS ISCII JIS X 0201 JIS X 0208 JIS X 0212 JIS X 0213 KOI-7 KPS 9566 KS X 1001 KS X 1002 LST 1564 LST 1590-4 PASCII Shift JIS SI 960 TIS-620 TSCII VISCII VSCII YUSCII
ISO/IEC 2022	ISO/IEC 8859 ISO/IEC 10367 Extended Unix Code / EUC
Mac OS Code pages ("scripts")	Armenian Arabic Barents Cyrillic Celtic Central European Croatian Cyrillic Devanagari Farsi (Persian) Font X (Kermit) Gaelic Georgian Greek Gujarati Gurmukhi Hebrew Iceland Inuit Keyboard Latin (Kermit) Maltese/Esperanto Ogham Roman Romanian Sámi Turkish Turkic Cyrillic Ukrainian VT100
DOS code pages	437 668 708 720 737 770 773 775 776 777 778 850 851 852 853 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 897 899 903 904 932 936 942 949 950 951 1040 1042 1043 1046 1098 1115 1116 1117 1118 1127 3846 ABICOMP CS Indic CSX Indic CSX+ Indic CWI-2 Iran System Kamenický Mazovia MIK
IBM AIX code pages	895 896 912 915 921 922 1006 1008 1009 1010 1012 1013 1014 1015 1016 1017 1018 1019 1046 1124 1133
Windows code pages	CER-GS 932 936 (GBK) 950 1169 Extended Latin-8 1250 1251 1252 1253 1254 1255 1256 1257 1258 1270 Cyrillic + Finnish Cyrillic + French Cyrillic + German Polytonic Greek
EBCDIC code pages	Japanese language in EBCDIC DKOI
DEC terminals (VTx)	Multinational (MCS) National Replacement (NRCS) French Canadian Swiss Spanish United Kingdom Dutch Finnish French Norwegian and Danish Swedish Norwegian and Danish (alternative) 8-bit Greek 8-bit Turkish SI 960 Hebrew Special Graphics Technical (TCS)
Platform specific	1052 1053 1054 1055 1056 1057 1058 Acorn RISC OS Amstrad CPC Apple II ATASCII Atari ST BICS Casio calculators CDC Compucolor 8001 Compucolor II CP/M+ DEC RADIX 50 DEC MCS/NRCS DG International Galaksija GEM GSM 03.38 HP Roman HP FOCAL HP RPL SQUOZE LICS LMBCS MSX NEC APC NeXT PETSCII PostScript Standard PostScript Latin 1 SAM Coupé Sega SC-3000 Sharp calculators Sharp MZ Sinclair QL Teletext TI calculators TRS-80 Ventura International WISCII XCCS ZX80 ZX81 ZX Spectrum
Unicode / ISO/IEC 10646	UTF-1 UTF-7 UTF-8 UTF-16 UTF-32 UTF-EBCDIC GB 18030 DIN 91379 BOCU-1 CESU-8 SCSU TACE16 Comparison of Unicode encodings
TeX typesetting system	Cork LY1 OML OMS OT1
Miscellaneous code pages	ABICOMP ASMO 449 Digital encoding of APL symbols ISO-IR-68 ARIB STD-B24 Fieldata HZ IEC-P27-1 INIS 7-bit 8-bit ISO-IR-169 ISO 2033 KOI KOI8-R KOI8-RU KOI8-U Mojikyō SEASCII Stanford/ITS Symbol TRON Unified Hangul Code
Control character	Morse prosigns C0 and C1 control codes ISO/IEC 6429 JIS X 0211 Unicode control, format and separator characters Whitespace characters
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