Installable Device Drivers

 An installable device driver lets you create a standard interface between
 DOS and an otherwise unsupported hardware device.  TECH Help! covers the
 following topics:

   Device Driver Basics ........  general introduction to device drivers

   Device Header Layout ........  data structure a the start of a driver
   Device Attribute ............  bit flags that define a device

   Device Requests .............  services a device driver must perform
   Device Request Header .......  layout of first part of a request packet
   Device Driver Errors ........  error codes a driver returns to DOS
   Device Status Word ..........  device status bit flags returned to DOS
   BPB: BIOS Parameter Block ...  a structure used by block devices

   IOCTL Functions .............  these communicate with a driver directly

   Mouse Support ...............  INT 33H fns are installed as a driver
   Expanded Memory Specification  EMM Fns are installed as a device driver
   DoubleSpace .................  disk-compression installed as a driver
   MRCI API ....................  disk-compression installed as a driver
   INT 2fH .....................  DOS extensions installed as drivers

See Also: CONFIG.SYS
          DOS Functions
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