The character sets used by Videotex are based, to greater or lesser extents, on ISO/IEC 2022. Three Data Syntax systems are defined by ITU T.101, corresponding to the Videotex systems of different countries.

Data Syntax 1

Data Syntax 1 is defined in Annex B of T.101:1994. It is based on the CAPTAIN system used in Japan. Its graphical sets include JIS X 0201 and JIS X 0208.

The following G-sets are available through ISO/IEC 2022-based designation escapes:

NameG-set escape type byteISO-IR for bytePrimary Character setSingle byte 94-code0x4A (J)ISO-IR-14 (JIS X 0201 Roman)Katakana Character setSingle byte 94-code0x49 (I)ISO-IR-13 (JIS X 0201 Kana)Mosaic I setSingle byte 94-code0x33 (3)(Occupies private-use byte; also registered as ISO-IR-137 with byte 0x79)Mosaic II setSingle byte 94-code0x63 (c)ISO-IR-71Display Control setSingle byte 96-code0x38 (8)(Occupies private-use byte)PDI setSingle byte 96-code0x57 (W)( byte exceptionally reserved and not used in ISO-IR)MVI setSingle byte 96-code0x39 (9)(Occupies private-use byte)Kanji setMultiple byte 94n-code0x42 (B)ISO-IR-87 (JIS X 0208:1983)Macro setSingle byte DRCS 96-code0x40 (@)(Uses a DRCS escape syntax)DRCS I setSingle byte DRCS 94-code0x41 (A)(Is a DRCS)DRCS II setMultiple byte DRCS 94n-code0x40 (@)(Is a DRCS)

Mosaic sets for Data Syntax 1

The mosaic sets supply characters for use in semigraphics.

� Not in Unicode

Data Syntax 2 Data Syntax 2 is defined in Annex C of T.101:1994. It corresponds to some European Videotex systems such as CEPT T/CD 06-01. The graphical character coding of Data Syntax 2 is based on T.51.

The default G2 set of Data Syntax 2 is based on an older version of T.51, lacking the non-breaking space, soft hyphen, not sign (¬) and broken bar (¦) present in the current version, but adding a dialytika tonos (΅—combining form is U+0344) at the beginning of the row of diacritical marks for combination with codes from a Greek primary set. An umlaut diacritic code distinct from the diaeresis code, as included in some versions of T.61, is also sometimes included.

The default G1 set is the second mosaic set, corresponding roughly to the second mosaic set of Data Syntax 1. The default G3 set is the third mosaic set, matching the first mosaic set of Data Syntax 1 for 0x60 through 0x6D and 0x70 through 0x7D, and otherwise differing. The first mosaic set matches the second except for 0x40 through 0x5E: 0x40 through 0x5A follow ASCII (supplying uppercase letters), whereas the remainder are national variant characters; the displaced full block is placed at 0x7F.

Representation of 0x5B-5E is not guaranteed in international communication and may be replaced by national application oriented variants. 0x5F may be displayed either as ⌗ (square) or _ (lower bar) to represent the terminator function required by Videotex services.

Data Syntax 3

Data Syntax 3 is defined in Annex D of T.101:1994. The graphical character coding of Data Syntax 3 is based on T.51.

The supplementary set for Data Syntax 3 is based on an older version of T.51, lacking the non-breaking space, soft hyphen, not sign (¬) and broken bar (¦) present in the current version, and allocating non-spacing marks for a "vector overbar" and solidus and several semigraphic characters to unallocated space in that set.

See the comments in the T.51 article for caveats about the combining mark Unicode mappings shown below. Unlike Unicode combining characters, T.51 diacritic codes precede the base character.

C0 control codes C0 control codes for Videotex differ from ASCII as shown in the table below. The , , (LS1), (LS0) and codes are also available in some or all data syntaxes, but without change in name or semantic from ASCII. Seq Dec Hex Replaced Syntaxes Acronym Name Description^H0808BS1, 2, 3APBActive Position Backward Moves cursor one position backward. If it is at the start of the line, moves it to the end of the line and back one line. This retains one possible semantic of the ASCII .^I0909HT1, 2, 3APFActive Position Forward Moves cursor one position forward. If it is at the end of the line, moves it to the start of the line and forward one line.^J100ALF1, 2, 3APDActive Position Down Moves cursor one line forward. If it is at the last line of the screen, moves it to the first line unless Data Syntax 3 scroll mode is active. This retains one possible semantic of the ASCII .^K110BVT1, 2, 3APUActive Position Up Moves cursor one line backward. If it is at the first line of the screen, moves it to the last line unless Data Syntax 3 scroll mode is active.^L120CFF1, 2, 3CSClear Screen Resets entire display to spaces with default display attributes and returns the cursor to its initial position. In Data Syntax 1, also resets macros and DRCS. This retains one possible semantic of the ASCII .^M130DCR1, 2, 3APRActive Position Return Moves the cursor to the start of the line. In Data Syntax 3, may instead move it to the start of the active field if it is entirely within it. This retains one possible semantic of the ASCII .^Q1711DC1/XON2CONCursor On Makes the cursor visible.^R1812DC22RPTRepeat Repeats the immediately preceding graphic character a number of times indicated by the low six bits of the following byte (from 0x40 to 0x7F).^T2014DC41KMCKey-In-Monitor Conceal Takes one parameter: 0x40 makes the key-in-monitor area unconcealed, 0x41 makes it concealed.2COFCursor Off Makes the cursor invisible.^X2418CAN1, 2, 3CANCancel In Data Syntax 2, fill the rest of the current line (after the current position) with spaces (compare ). In Data Syntax 1 and 3, immediately stop all running macros. Contrast the semantic of basic ASCII .^Y2519EM1, 2, 3SS2Single Shift Two .^Z261ASUB3SDCService Delimitor Character Implementation-defined but non-presentational.^\281CFS1, 3APSActive Position Set Followed by two bytes (from 0x40 to 0x7F; may also be from 0xA0 to 0xFF in Data Syntax 3) respectively giving a row and column address in their low six bits. Compare and .^]291DGS1, 2, 3SS3Single Shift Three .^^301ERS1, 2, 3APHActive Position Home Returns cursor to the initial position.^_311FUS1, 3NSRNon-Selective Reset Resets all display attributes (including ISO 2022 state, domain, text parameters, textures, colour mode but not macros, DRCS or programmable masks), then moves the cursor to a specified position. Followed by two bytes (from 0x40 to 0x7F; may also be from 0xA0 to 0xFF in Data Syntax 3) respectively giving a row and column address in their low six bits. Compare .2APAActive Position Address Followed by two or four bytes (from 0x40 to 0x7F) giving a row and column address in their low six bits. Four bytes are used if there are more than 63 rows and columns, with the most significant six bits being first for each parameter. Compare and . If the following byte is not in the range of 0x40 to 0x7F, indicates a switch to another coding scheme (contrast ).

C1 control codes The following specialised C1 control codes are used in Videotex. There are four registered sets, with some differences between them.