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.