@node biosdisk, bios
@subheading Syntax

@example
#include <bios.h>

int biosdisk(int cmd, int drive, int head, int track,
	     int sector, int nsects, void *buffer);
@end example

@subheading Description

This function interfaces with the BIOS disk service (interrupt 0x13).
Please refer to a BIOS reference manual for detailed information about
the parameters of this call.  The function assumes a sector size of 512
bytes.

The following functions of Int 13h are currently supported:

@table @asis
@item 0 - reset disk subsystem
@item 1 - get status of last operation (see @ref{_bios_disk}, for possible values)
@item 2 - read one or more sectors
@item 3 - write one or more sectors
@item 5 - format a track
@item 6 - format a cylinder and set bad sector flag
@item 7 - format drive from specified cylinder
@item 8 - get drive parameters
@item 9 - initialize drive parameters
@item 10 - read long sectors
@item 11 - write long sectors
@item 12 - seek to cylinder
@item 13 - alternate fixed disk reset
@item 14 - read sector buffer
@item 15 - write sector buffer
@item 16 - test for drive ready
@item 17 - recalibrate drive
@item 18 - controller RAM diagnostic
@item 19 - controller drive diagnostic
@item 20 - controller internal diagnostic
@item 21 - get DASD type
@item 22 - read disk change line status
@item 23 - set DASD type (pass DASD code in @var{nsects})
@item 24 - set media type for format
@end table

The first request with more sectors than will fit in the transfer
buffer will cause a DOS buffer to be allocated.  This buffer is
automatically freed when your application exits.  Requests for more
sectors than 18 sectors (9K) will fail.

Function 8 returns values in @var{buffer} as follows:

@table @asis
@item byte 0 = sectors per track (bits 0..5), top two bits of cylinder (in bits 6..7)
@item byte 1 = cylinders (bits 0..7)
@item byte 2 = number of drives
@item byte 3 = number of heads
@end table

@subheading Return Value

The value of AH returned by the BIOS.  See @ref{_bios_disk}, for a
detailed list of possible status and error codes.

@subheading Portability

@portability !ansi, !posix

@subheading Example

@example
char buffer[512];
if (biosdisk(2, 0x80, 0, 0, 0, 1, buffer))
  error("disk");
@end example