Error codes returned in AX, when CY=1:

        DOS ver.   AX     Text
        --------------------------------------------------------------
          2.x      01     Function number invalid
          2.x      02     File not found
          2.x      03     Path not found
          2.x      04     Too many open files
          2.x      05     Access denied
          2.x      06     Invalid handle
          2.x      07     Memory control block destroyed
          2.x      08     Insufficient memory
          2.x      09     Memory block address invalid
          2.x      0A     Environment invalid
          2.x      0B     Format invalid
          2.x      0C     Access code invalid
          2.x      0D     Data invalid
          2.x      0F     Invalid drive
          2.x      10     Attempted to remove current directory
          2.x      11     Not same device
          2.x      12     No more files
          3.x      13     Disk write-protected
          3.x      14     Unknown unit
          3.x      15     Drive not ready
          3.x      16     Unknown command
          3.x      17     Data error (CRC)
          3.x      18     Bad request structure length
          3.x      19     Seek error
          3.x      1A     Unknwon media type
          3.x      1B     Sector not found
          3.x      1C     Printer out of paper
          3.x      1D     Write fault
          3.x      1E     Read fault
          3.x      1F     General failure
          3.x      20     Sharing violation
          3.x      21     Lock violation
          3.x      22     Disk change invalid
          3.x      23     FCB unavailable
          3.x      24     Sharing buffer overflow
          3.x      25     Reserved
          4.x      26     Unable to complete file operation
          3.x      27-31   Reserved
          3.x      32     Network request not supported
          3.x      33     Remote computer not listening
          3.x      34     Duplicate name on network
          3.x      35     Network path not found
          3.x      36     Network busy
          3.x      37     Network device no longer exists
          3.x      38     Network BIOS command limit exceeded
          3.x      39     Network adapter hardware error
          3.x      3A     Incorrect response from network
          3.x      3B     Unexpected network error
          3.x      3C     Incompatible remote adapter
          3.x      3D     Print queue full
          3.x      3E     Not enough space to print file
          3.x      3F     Print file was cancelled
          3.x      40     Network name was deleted
          3.x      41     Network: Access denied
          3.x      42     Network device type incorrect
          3.x      43     Network name not found
          3.x      44     Network name limit exceeded
          3.x      45     Network BIOS session limit exceeded
          3.x      46     Sharing temporarily paused
          3.x      47     Network request not accepted
          3.x      48     Print/disk redirection paused
          3.x      49-4F  Reserved
          3.x      50     File exists
          3.x      51     Reserved
          3.x      52     Cannot make directory
          3.x      53     Fail on INT 24h
          4.x      54     Too many redirections
          4.x      55     Duplicate redirection
          4.x      56     Invalid password
          4.x      57     Invalid parameter
          4.x      58     Network data fault
          4.x      59     Function not supported by network
          4.x      5A     Required system component not installed

      Error Classes:
                   01     Out of resource. Example: Out of space
                          or out of channals.
                   02     Temporary situation. Something expected to
                          disappear with time. This is not an error
                          condition, but a temporary situation such
                          as a locked file.
                   03     Authorization: Permission problem
                   04     Internal: Internal error in system software.
                          Probable problem with system software, rather
                          than a user a system failure.
                   05     Hardware failure: A serious problem not
                          the fault of user program.
                   06     System failure. Serious failure of system
                          software not the fault of the user, such as
                          missing or incorrect configuration files.
                   07     Application program error: Inconsistent
                          requests.
                   08     Not found: File or item not found.
                   09     Bad format: File or value invalid format or
                          type; unsuitable.
                   0A     Locked: Locked file or item
                   0B     Media error: Media failure such as incorrent
                          disk, CRC error, defective media.
                   0C     Already exists: Duplication error, such as
                          declaring a macinename that already exists.
                   0D     Unknown
      Suggested Action:
                   01     Retry. Retry a few times, then prompt the user
                          if the program should be terminated.
                   02     Delayed retry: Retry several time, with delay
                          in between, then prompt the user if the program
                          should be terminated.
                   03     Prompt user. Ask the user to correct the infor-
                          mation.
                   04     Abort after cleanup. DOS is in a orderly state,
                          so it's safe to cleanup, before termination.
                   05     Immediate abort. Stop application immidiately,
                          without clearing regsiters or anything else.
                          Don't write to or close any files, just abort
                          the program (this is serious)!
                   06     Ignore
                   07     Retry after user intervention. Ask the user to
                          perform some action, such as inserting a disk
                          etc. Then retry the operation.
      Error Locus:
                   01     Unknown or not appropriate
                   02     Block device
                   03     Network related
                   04     Serial device
                   05     Memory related