## Display Device Driver Reference for OS/2

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### Design of Installable Virtual Video Device Drivers

A virtual video device driver is a base device driver, although a "DEVICE=" statement in the CONFIG.SYS file is used to specify one or more virtual video device drivers to load. The DOS Session Manager and DOS Session Window Manager identify a virtual video device driver by its registered name. For example, a virtual video device driver for the primary display would register as VVIDEO1$; a virtual video device driver for the secondary display device would register as VVIDEO2$; and so forth.

Note: Support of multiple DOS sessions is disabled if no virtual video device driver claims ownership of the primary display device after virtual video device driver loading and initialization is completed.