Compatibility: 2.0+
Expects: AH    3bH
DS:DX address of an ASCIIZ  string of a directory name
                                                                  
Returns: AX    error code if CF is set to CY
                                                                  
Info: Selects a default directory for a drive.

DS:DX points to an ASCIIZ string in the form...
d:\path\dirname 0 
...which identifies the directory to become the default.  If the
d: portion is missing, the \path\dirname is assumed to be on the
current default drive; see Fn 0EH (set default drive).

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

Notes:   This selects the default directory for the specified or current
drive.  it DOES NOT select a default drive.
  If drive and/or leading path are omitted, defaults are assumed.
  The maximum length of the ASCIIZ string is 64 bytes.

- -

DOS Fn 3bH: Set DOS Default Directory -- CHDIR