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The MS-DOS Encyclopedia

Appendix B: Critical Error Codes

    Critical errors are returned via Interrupt 24H. If register AL bit 7
    is 0, then the error was a disk error; if register AL bit 7 is 1, then
    the error was a nondisk error. The upper half of DI is undefined; the
    lower half of DI contains one of the following error-condition codes:

    Code      Description
    00H       Attempt to write on write-protected disk
    01H       Unknown drive or unit
    02H       Drive not ready
    03H       Invalid command
    04H       Data error (CRC failed)
    05H       Bad request structure length
    06H       Seek error
    07H       Unknown media type
    08H       Sector not found
    09H       Printer out of paper
    0AH       Write fault
    0BH       Read fault
    0CH       General failure
    0FH       Invalid disk change

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