Compatibility: 2.0+
Expects: AX    4301H
CX    file attribute to assign to the file
DS:DX address of an ASCIIZ  string of a filespec 
                                                                  
Returns: AX    error code if CF is set to CY
                                                                  
Info: Sets the file attribute of a file or directory.

DS:DX points to an ASCIIZ string in the form...
d:\path\filename.ext 0 
...which identifies the location and name of the file.  It must
not contain wildcards , but it may identify a directory name.

If CF is set on return, an error code is in AX and no action was
taken.

Notes:   To add an attribute to an existing value, use fn 4300H to
obtain the current setting, OR the desired new attribute bit,
then call this function.

  Bits 3 and 4 of CX (volume label and directory) must be clear
when calling this function.  If you wish to hide a directory,
use CX=02H (not 12H as you might expect).

See Also: Fn 4300H (query file attributes)
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DOS Fn 4301H: Set File Attribute