Indian Script Code for Information Interchange

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Indian Script Code for Information Interchange (ISCII) is a coding scheme for representing various writing systems of India. It encodes the main Indic scripts and a Roman transliteration. The supported scripts are: Bengali–Assamese, Devanagari, Gujarati, Gurmukhi, Kannada, Malayalam, Oriya, Tamil, and Telugu. ISCII does not encode the writing systems of India that are based on Persian, but its writing system switching codes nonetheless provide for Kashmiri, Sindhi, Urdu, Persian, Pashto and Arabic. The Persian-based writing systems were subsequently encoded in the PASCII encoding.

ISCII has not been widely used outside certain government institutions, although a variant without the ATR mechanism was used on classic Mac OS, Mac OS Devanagari,[1] and it has now been rendered largely obsolete by Unicode. Unicode uses a separate block for each Indic writing system, and largely preserves the ISCII layout within each block.

Background[edit]

The Brahmi-derived writing systems have similar structure. So ISCII encodes letters with the same phonetic value at the same code point, overlaying the various scripts. For example, the ISCII codes 0xB3 0xDB represent [ki]. This will be rendered as കി in Malayalam, कि in Devanagari, as ਕਿ in Gurmukhi, and as கி in Tamil. The writing system can be selected in rich text by markup or in plain text by means of the ATR code described below.

One motivation for the use of a single encoding is the idea that it will allow easy transliteration from one writing system to another. However, there are enough incompatibilities that this is not really a practical idea.

ISCII is an 8-bit encoding. The lower 128 code points are plain ASCII, the upper 128 code points are ISCII-specific. In addition to the code points representing characters, ISCII makes use of a code point with mnemonic ATR that indicates that the following byte contains one of two kinds of information. One set of values changes the writing system until the next writing system indicator or end-of-line. Another set of values select display modes such as bold and italic. ISCII does not provide a means of indicating the default writing system.

Codepage layout[edit]

The following table shows the character set for Devanagari. The code sets for Assamese, Bengali, Gujarati, Gurmukhi, Kannada, Malayalam, Oriya, Tamil, and Telugu are similar, with each Devanagari form replaced by the equivalent form in each writing system. Each character is shown with its decimal code and its Unicode equivalent.

ISCII Devanagari
0 1 2 3 4 5 6 7 8 9 A B C D E F
0x NUL SOH STX ETX EOT ENQ ACK BEL  BS   HT   LF   VT   FF   CR   SO   SI  
1x DLE DC1 DC2 DC3 DC4 NAK SYN ETB CAN  EM  SUB ESC  FS   GS   RS&   US 
2x  SP  ! " # $ % & ' ( ) * + , - . /
3x 0 1 2 3 4 5 6 7 8 9 : ; < = > ?
4x @ A B C D E F G H I J K L M N O
5x P Q R S T U V W X Y Z [ \ ] ^ _
6x ' a b c d e f g h i j k l m n o
7x p q r s t u v w x y z { | } ~ DEL
8x
9x
Ax
Bx
Cx य़
Dx INV ि
Ex ATR
Fx EXT
  Undefined
  Lead byte

Special code points[edit]

INV character—code point D9 (217)
The INV (invisible consonant) character is used as a pseudo-consonant to display combining elements in isolation. For example, क (ka) + ् (halant) + INV = क्‍ (half ka). The Unicode equivalent is U+200D ZERO WIDTH JOINER (ZWJ). However, as noted below, the ISCII halant character can be doubled or combined with the ISCII nukta to achieve effects created by ZWNJ or ZWJ in Unicode. For this reason, Apple maps the ISCII INV character to the Unicode left-to-right mark, so as to guarantee round-tripping.[1]
ATR character—code point EF (239)
The ATR (attribute) character followed by a byte code is used to switch to a different font attribute (such as bold) or to a different ISCII or PASCII language (such as Bengali), up to the next ATR sequence or the end of the line. This has no direct Unicode equivalent, as font attributes are not part of Unicode, and each script has a distinct set of code points.
Presentational attributes
ATR + byte Mnemonic Formatting option
0x30 BLD Bold
0x31 ITA Italics
0x32 UL Underlining
0x33 EXP Expanded
0x34 HLT Highlight
0x35 OTL Outline
0x36 SHD Shadow
0x37 TOP Top half of character (used with LOW to create double-height characters)
0x38 LOW Bottom half of character (used with TOP to create double-height characters)
0x39 DBL Entire row double-width and double-height
Shifts to ISCII scripts
ATR + byte Mnemonic ISCII script
0x40 DEF Default script (i.e. the script which will be switched back to after a line break)
0x41 RMN Romanised transliteration
0x42 DEV Devanagari
0x43 BNG Bengali script
0x44 TML Tamil script
0x45 TLG Telugu script
0x46 ASM Assamese script
0x47 ORI Odia script
0x48 KND Kannada script
0x49 MLM Malayalam script
0x4A GJR Gujarati script
0x4B PNJ Gurmukhī
Shifts to PASCII
ATR + byte Mnemonic PASCII locale
0x71 ARB Arabic alphabet
0x72 PES Persian alphabet
0x73 URD Urdu alphabet
0x74 SND Sindhi alphabet
0x75 KSM Kashmiri alphabet
0x76 PST Pashto alphabet
EXT character—code point F0 (240)
The EXT (extensions for Vedic) character followed by a byte code indicates a Vedic accent. This has no direct Unicode equivalent, as Vedic accents are assigned to distinct code points.
Halant character ्—code point E8 (232)
The halant character removes the implicit vowel from a consonant and is used between consonants to represent conjunct consonants. For example, क (ka) + ् (halant) + त (ta) = क्त (kta). The sequence ् (halant) + ् (halant) displays a conjunct with an explicit halant, for example क (ka) + ् (halant) + ् (halant) + त (ta) = क्‌त. The sequence ् (halant) + ़ (nukta) displays a conjunct with half consonants, if available, for example क (ka) + ् (halant) + ़ (nukta) + त (ta) = क्‍त.
Correspondences between ISCII and Unicode halent/virama behaviour
ISCII Unicode
single halant E8 halant 094D
halant + halant E8 E8 halant + ZWNJ 094D 200C
halant + nukta E8 E9 halant + ZWJ 094D 200D
Nukta character ़—code point E9 (233)
The nukta character after another ISCII character is used for a number of rarer characters which don't exist in the main ISCII set. For example क (ka) + ़ (nukta) = क़ (qa). These characters have precomposed forms in Unicode, as shown in the following table.
Single Unicode characters corresponding to ISCII nukta sequences
ISCII
code point
Original
character
Character
with nukta
Unicode
code point
A1 (161) 0950
A6 (166) 090C
A7 (167) 0961
AA (176) 0960
B3 (179) क़ 0958
B4 (180) ख़ 0959
B5 (181) ग़ 095A
BA (186) ज़ 095B
BF (191) ड़ 095C
C0 (192) ढ़ 095D
C9 (201) फ़ 095E
DB (219) ि 0962
DC (220) 0963
DF (223) 0944
EA (234) 093D

Code pages for ISCII conversion[edit]

To convert from Unicode (UTF-8) to an ISCII / ANSI coding, the following code pages may be used:

  • 57002: Devanagari (Hindi, Marathi, Sanskrit, Konkani)
  • 57003: Bengali
  • 57004: Tamil
  • 57005: Telugu
  • 57006: Assamese
  • 57007: Odia
  • 57008: Kannada
  • 57009: Malayalam
  • 57010: Gujarati
  • 57011: Punjabi (Gurmukhi)

Code points for all languages[edit]

References[edit]

  1. ^ a b Apple (2005-04-05) [1998-02-05]. "Map (external version) from Mac OS Devanagari encoding to Unicode 2.1 and later". Unicode Consortium.

External links[edit]