Virtual Device Drivers

The OS/2 2.0 operating system allows more than one active application at a time. The operating system has VDDs that manage shared access to hardware input and output (I/O) devices for multiple DOS or WIN-OS/2 sessions. Devices with VDD support include the keyboard, mouse, and serial and parallel ports.

Virtual device drivers:

The following VDDs are provided with the OS/2 2.0 operating system:

VDD DESCRIPTION
VBIOS ROM BIOS support
VCMOS CMOS data area and Real Time Clock support
VCOM Asynchronous communication ports
VDMA Direct Memory Access
VDSK Disk (only for INT 13 copy-protection)
VKBD Keyboard
VLPT Printer
VMSE Mouse
VNPX Numeric Processor Extension (80387)
VPIC Programmable Interrupt Controller
VTIMER Timer
VVIDEO Video (VCGA, MCGA, VEGA, VVGA, V8514)
VXMS Extended Memory Support
VEMM Expanded Memory Support

By using DEVICE= statements in the CONFIG.SYS file, similar to physical device drivers, VDDs are installed when the OS/2 2.0 operating system starts. For example, the following CONFIG.SYS statement installs the VCOM VDD:

  DEVICE=C:\OS2\MDOS\VCOM.SYS

VCOM.SYS communicates with the COM.SYS physical device driver to provide virtual RS-232 asynchronous communications support in the DOS session.