## Display Device Driver Reference for OS/2

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### Built-in Extended INT 10h and INT 2Fh Services

The EGA Register interface is integrated into the virtual video device driver as part of its INT 10h interception logic. This interface is a set of INT 10h services that are used by applications to make possible drawing operations and simultaneous use of the mouse pointer on EGA and VGA hardware. The virtual video device driver's pointer drawing services are intended to replace this interface, but existing graphical applications still use it (generally when mouse support is also present). The interface must be present or these applications will not function correctly.

The INT 2Fh services notify applications when they are about to be switched to full-screen or background mode. Applications can use this notification to stop accessing video memory if they are using a video memory not supported for background operation. This prevents them from freezing and redraws their screen in the event the virtual video device driver fails to fully restore it.

    /--- IMPLEMENTATION NOTE ----------------------------------\

    |                                                          |

    |   The EGA Register interface has not been integrated     |

    |   into the virtual video device drivers. Until and       |

    |   unless this is done, EGA.SYS must be supplied with     |

    |   the system and loaded by EGA/VGA users on an           |

    |   as-needed basis.                                       |

    |                                                          |

    \----------------------------------------------------------/