## Virtual Device Driver Reference for OS/2

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### Direct I/O Access

The virtual parallel port device driver, at its initialization, registers an Inter-device Driver Communication (IDC) with the physical parallel port device driver. The VLPT requests exclusive access to the parallel port hardware through the VDD/PDD IDC when a DOS application interfaces directly with the hardware. Data transmitted using the direct I/O access method will bypass the spooler. Completion of exclusive access occurs when the key combination Ctrl+Alt+Print Screen is pressed, the application is terminated , or the DOS session is terminated.