## Display Device Driver Reference for OS/2

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### EGA Register Interface

The EGA register interface is a library of ten functions supported for a DOS session, advanced graphics applications (modes D, E, F, and 10). These functions do the following:

Read from, or write to, one or more of the EGA write-only registers

Define default values for the EGA write-only registers, reset the EGA registers to these default values, or return the default values

Check whether the EGA register interface is present and, if so, return its version number.

When the application uses the EGA register interface, OS/2 2.1 maintains a backup copy or shadows how the EGA registers are set. Then, if the operator switches away from (and later returns to) the application, the registers are restored properly. It is not necessary to use the EGA register interface to set the mode, color palette, or palette registers. Instead, use ROM BIOS function INT 10h with AH = 00h, 0Bh, or 10h, respectively.