Type Specification

When you open an existing character set, these settings should already be set appropriately. You usually do not need to change these settings.

A character set can be:

• ASCII_BASED: The ASCII character set defines 128 characters (0 to 127 decimal, 0 to FF hexadecimal, and 0 to 177 octal) that are used in English text.
• EBCDIC_BASED: The EBCDIC character set is an IBM mainframe encoding scheme that contains characters similar to the ASCII characters. It contains non-contiguous letter sequences and control code values from 0 to 63 but lacks several ASCII punctuation marks.
• FIXED_WIDTH: Ideographic languages like Chinese need multibyte encoding schemes. In a fixed-width, multibyte encoding scheme, each character is represented by a fixed number of bytes (at least 2 bytes).

NOTE: Fixed-width character sets are not supported in this release. This button is provided for backward compatibility.

Additional Flags

DISPLAY: A character set that has the display flag set is used by certain clients to display alphabets such as Arabic and Hebrew. The character set is used only for display and not for storing data. Display character sets have additional characteristics. See Extended Character Classification, Shape Table, and Ligature.

SHIFT: Some variable-width encoding schemes use the shift-in as a control code to signal that a range of characters is single-byte, for example, until the shift-out code is encountered. The shift-out code would signal that the next group of characters is double-byte, for example.

BYTE_UNIQUE: A byte-unique character set has a specific code range for single-byte characters and a specific code range for multibyte characters. Thus, in a byte-unique character set, the code in the first byte indicates whether the character is single-byte or multibyte. A character set that is all single-byte (such as US7ASCII) or all multibyte (such as Asian character sets) is byte-unique by default.

Special Characters in Fixed-Width Character Sets

The single-byte space, underscore, and percent characters are not present in fixed-width character sets and must be specified:

• Pad Character: Used to pad a string to the desired display length. Typically a space.
• Underscore Character: Used in pattern-matching to match exactly one character. For example, oracle matches the oracl_ pattern.
• Percent Character: Used in pattern-matching to match 0 or more characters. For example, to find all employees whose names begin with SM, use the SM% pattern.

Shift Characters

If the SHIFT flag is set, then the code and the glyph for the Shift Out and Shift In characters are defined in these fields.

7-Bit Display Character Sets

This field designates whether a display character set has a 7-bit encoding scheme.