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Synopsis:
    #include <bios.h>
    unsigned short _bios_disk( unsigned service,
                               struct diskinfo_t *diskinfo );
    struct  diskinfo_t {        /* disk parameters   */
            unsigned drive;     /* drive number      */
            unsigned head;      /* head number       */
            unsigned track;     /* track number      */
            unsigned sector;    /* sector number     */
            unsigned nsectors;  /* number of sectors */
            void __far *buffer; /* buffer address    */
    };

Description:
    The _bios_disk function uses INT 0x13 to provide access to the BIOS disk
    functions.  Information for the desired service is passed the
     diskinfo_t structure pointed to by diskinfo.  The value for service can
    be one of the following values:

    Value     Meaning

_DISK_RESET
    Forces the disk controller to do a reset on the disk.  This request does
    not use the diskinfo argument.

_DISK_STATUS
    Obtains the status of the last disk operation.

_DISK_READ
    Reads the specified number of sectors from the disk.  This request uses
    all of the information passed in the diskinfo structure.

_DISK_WRITE
    Writes the specified amount of data to the disk.  This request uses all
    of the information passed in the diskinfo structure.

_DISK_VERIFY
    Checks the disk to be sure the specified sectors exist and can be read.
    A CRC (cyclic redundancy check) test is performed.  This request uses
    all of the information passed in the diskinfo structure except for the
    buffer field.

_DISK_FORMAT
    Formats the specified track on the disk.  The head and track fields
    indicate the track to be formatted.  Only one track can be formatted per
    call.  The buffer field points to a set of sector markers, whose format
    depends on the type of disk drive.  This service has no return value.

    This function is not supported by DOS/4GW (you must use the Simulate
    Real-Mode Interrupt DPMI call).

Returns:
    The _bios_disk function returns status information in the high-order
    byte when service is _DISK_STATUS, _DISK_READ, _DISK_WRITE, or
    _DISK_VERIFY.  The possible values are:

    Value     Meaning

0x00
    Operation successful

0x01
    Bad command

0x02
    Address mark not found

0x03
    Attempt to write to write-protected disk

0x04
    Sector not found

0x05
    Reset failed

0x06
    Disk changed since last operation

0x07
    Drive parameter activity failed

0x08
    DMA overrun

0x09
    Attempt to DMA across 64K boundary

0x0A
    Bad sector detected

0x0B
    Bad track detected

0x0C
    Unsupported track

0x10
    Data read (CRC/ECC) error

0x11
    CRC/ECC corrected data error

0x20
    Controller failure

0x40
    Seek operation failed

0x80
    Disk timed out or failed to respond

0xAA
    Drive not ready

0xBB
    Undefined error occurred

0xCC
    Write fault occurred

0xE0
    Status error

0xFF
    Sense operation failed


Example:
    #include <stdio.h>
    #include <bios.h>

    void main()
      {
        struct diskinfo_t di;
        unsigned short status;

        di.drive = di.head = di.track = di.sector = 0;
        di.nsectors = 1;
        di.buffer = NULL;
        status = _bios_disk( _DISK_VERIFY, &di );
        printf( "Status = 0x%4.4X\n", status );
      }

Classification:
    BIOS

Systems:
    DOS, Windows, Win386