Reference Manual

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Creating the UCM File

The UCM file maps the relationship between Unicode characters and hexadecimal values in the code page.

Edit the UCM file in a text editor. The file must contain only 7-bit ASCII characters on Linux, UNIX, and Windows systems, or the equivalent characters on EBCDIC systems.

The following table shows valid values for the precision indicator:

Precision Indicator	Description
0	Normal, round-trip mapping. A character retains the same hexadecimal value after being copied from the code page to Unicode and then copied back to the code page again.
1	Fallback mapping. A character is copied from Unicode to the code page but not back to Unicode again. If a character was copied back to Unicode again, it would get a new Unicode value.
2	Invalid character. The character will be replaced by the substitution character.
3	Reverse-fallback mapping. A character is copied from the code page to Unicode but not back to the code page. If the character was copied back to the code page again, it would get a different hexadecimal value.

Most characters are defined as round-trip mappings and have Unicode or hexadecimal values.

Sometimes, however, it is necessary to use one-way mappings, which cause an overlap between characters. For example, if a character is in the source code page but not in the target code page, or if a character is invalid, you can define a reverse-fallback mapping for it. When PowerExchange reads the data, the reverse-fallback mapping causes the character to be changed to a Unicode character that is a near match.

For more information about UCM file format, see the following Web site: http://icu.sourceforge.net/userguide/conversion-data.html#ucmformat.

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Reference Manual

Reference Manual

Creating the UCM File

Creating the UCM File