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biosdisk
========

Syntax
------

     #include <bios.h>
     
     int biosdisk(int cmd, int drive, int head, int track,
                 int sector, int nsects, void *buffer);

Description
-----------

This function interfaces with the BIOS disk sevice (interrupt 0x13).
Please refer to a BIOS reference manual for detailed information about
the parameters of this call.  All known calls are supported.  A sector
size of 512 bytes is assumed.

0 - reset disk subsystem
1 - get disk subsystem status
2 - read one or more sectors
3 - write one or more sectors
5 - format a track
6 - format back track
7 - format drive
8 - get drive parameters
9 - initialize drive parameters
10 - read long sectors
11 - write long sectors
12 - seek to cylinder
13 - alternate fixed disk reset
14 - read test buffer
15 - write test buffer
16 - test for drive ready
17 - recalibrate drive
18 - controller RAM diagnostic
19 - controller drive diagnostic
20 - controller internal diagnostic
15 - read fixed disk type
22 - read disk change line status
23 - set DASD type (pass dasd in NSECTS)
24 - set media type for format

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.  Since this buffer is
big enough to hold 18 sectors, requests for more sectors than that will
fail.

Request eight returns values in buffer as follows:

byte 0 = sectors per track (bits 0..5) and top two bits of cylinder (in bits 6..7)
byte 1 = cyliders (bits 0..7)
byte 2 = number of drives
byte 3 = number of heads

Return Value
------------

The value of AH returned by the BIOS.

Example
-------

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