DDS for display files
The following section describes, by position, DDS for describing display
files. Positions not mentioned have no special considerations for
Unicode.
Length (positions 30 through 34):
Specify the length of the field in these positions. The length of a
field containing Unicode data can range from 1 through 16 381 code
units.
When determining the program length of a field containing Unicode data,
consider the following:
- Each Unicode code unit is 2 bytes long.
- The program length of the field is specified in number of Unicode code
units. For example, a field containing 3 Unicode code units has 6 bytes
of data.
- The field's default display length is equal to the field's
program length or 2 times the number of Unicode code units.
- After converting between Unicode data and EBCDIC, the resulting data may
be equal to, longer or shorter than the original length data before the
conversion, depending upon the CCSID of the device. For example, 1
Unicode code unit is composed of 2 bytes of data. That code unit might
convert to 1 SBCS character composed of 1 byte of data, 1 graphic-DBCS
character composed of 2 bytes of data, or 1 bracketed DBCS character composed
of 4 bytes of data.
- The field's display length can be specified separately from the
program length by using the alternate-field-length parm on the CCSID
keyword.
Data type (position 35):
The only valid data type for Unicode data is the G data type.
- G (Graphic)
- Type G in combination with the CCSID keyword to specify this field
contains Unicode data.
Normally, by specifying G, the field would contain graphic-DBCS
data. In combination with the CCSID keyword, the field now contains
Unicode data. On output, the data is mapped to corresponding characters
in the CCSID that the device is configured as. On input, the data is
mapped to corresponding Unicode code units.
Decimal positions (positions 36 and 37):
Leave these positions blank when using Unicode data.
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