Int 21 Fn 3B  - Dos 2+ - "chdir" - Set Current Directory                   [D]

   AH = 3Bh
   DS:DX -> ASCIZ pathname to become current directory (max 64 bytes)

Return: CF clear if successful
       AX destroyed
   CF set on error
       AX = error code (03h) (see #1366 at AH=59h/BX=0000h)

Notes: if new directory name includes a drive letter, the default drive is
     not changed, only the current directory on that drive
   changing the current directory also changes the directory in which
     FCB file calls operate
   under the FlashTek X-32 DOS extender, the pointer is in DS:EDX

See Also: AH=47h,AX=713Bh,INT 2F/AX=1105h