## Virtual Device Driver Reference for OS/2

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### INT 7Fh Support

To access the touch-sensitive display device, DOS applications use the software interrupt 7Fh (INT 7Fh) interface. OS/2 applications use the Tou xxx API. The virtual touch-sensitive device driver provides this by using a standard DOS session software interrupt hook. This virtual device driver runs in protect mode (which allows it to share code in all DOS sessions) and virtualizes all the hardware-dependent features that the INT 7Fh interface provides (for example, changing thresholds).

In addition to the touch-sensitive device capability, it is also possible to use the touch-sensitive display to emulate the IBM* mouse. In this case, the standard mouse INT 33h API (for DOS) is used.

Note that only DOS sessions running full screen can obtain full touch XYZ data. Windowed DOS sessions running under Presentation Manager are restricted to emulated mouse data. A DOS touch application that started as full screen stops receiving touch data if it is switched to a window, and starts receiving data again if it switched back to full screen. Conversely, a DOS touch application that is started in a window does not receive data until it is switched to full screen, and does not stop receiving data until it is switched back to a window.