File Management - IBM

Processing double-byte characters
Due to the large number of double-byte characters, the system needs more
information to identify each double-byte character than is needed to identify each
alphanumeric character.
There are two types of double-byte characters: basic and extended. These
characters are usually processed by the device on which the characters are
displayed or printed.
Basic double-byte characters
Basic characters are frequently used double-byte characters that reside in the
hardware of a DBCS-capable device. The number of double-byte characters stored
in the device varies with the language supported and the storage size of the
device. A DBCS-capable device can display or print basic characters without using
the extended character processing function of the operating system.
Extended double-byte characters
When processing extended characters, the device requires the assistance of the
system. The system must tell the device what the character looks like before the
device can display or print the character. Extended characters are stored in a DBCS
font table, not in the DBCS-capable device. When displaying or printing extended
characters, the device receives them from the DBCS font table under control of the
operating system.
Extended character processing is a function of the operating system that is required
to make characters stored in a DBCS font table available to a DBCS-capable device.
To request extended character processing, specify the double-byte extended
character parameter, IGCEXNCHR(*YES), on the file creation command when you
create a display (CRTDSPF command) or printer file (CRTPRTF command) that
processes double-byte data. Because IGCEXNCHR(*YES) is the default value, the
system automatically processes extended characters unless you instruct it
otherwise. You can change this file attribute by using a change file (CHGDSPF or
CHGPRTF) or override file (OVRDSPF or OVRPRTF) command. For example, to
override the display file DBCSDSPF so that extended characters are processed,
enter:
OVRDSPF DSPF(DBCSDSPF) IGCEXNCHR(*YES)
Notes:
1. The system ignores the IGCEXNCHR parameter when processing alphanumeric
files.
2. When you use the Japanese 5583 Printer to print extended characters, you must
use the Kanji print function of the Advanced DBCS Printer Support for AS/400
licensed program. Refer to the Kanji Print Function User’s Guide and Reference for
how to use this utility.
What happens when extended double-byte characters are not
processed
When extended characters are not processed, the following happens:
v Basic double-byte characters are displayed and printed.
Appendix B. Double-byte character set support 203