DOS Device Drivers

   DOS Devices may be accessed by Int 21 Function calls which support file I/O
by specifying the name of a device rather than a file or by useing the Handle
Read and Write functions with the STDIN, STDOUT, and STDERR devices which are
set to handles 0, 1, and 2 respectfully when dos loads any program. Some Device
drivers also add new Interrupt Functions to the DOS or BIOS.

   Console Input and Output
   Clock device
   Physical Communication Drivers
   Logical Communication Device
   Physical Printer
   Logical Printer


see also:
BIOS Device Drivers
Handle Close Int\21F\3E
Handle Open Int\21f\3D
Handle Read Int\21f\3F
Handle Write Int\21f\40
IOCTL

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