## Display Device Driver Reference for OS/2

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### Overview of Modifications

There are two kinds of modifications to consider:

Modifications to the display hardware

Modifications to implement enabling of DBCS, which allows the DBCS characters to be displayed on the screen

There are three types of character sets:

DBCS (Double-Byte Character Set)-2-byte Kanji, Hiragana, and Katakana (etc .) character set

SBCS (Single-Byte Character Set)-1-byte alphanumeric (and special characters) character set

MBCS (Mixed-Byte Character Set)-character set containing both DBCS and SBCS characters

Hardware modifications are required when developing a PM display driver for a display card that is not supported by the IBM PM display drivers. If the developer models the display driver design on the VGA/SVGA drivers supplied , then further modifications for DBCS enabling are not necessary because these are provided in the device-independent component.