Int 2F Fn 1201  U - DOS 3+ Internal - Close Current File                   [D]

   AX = 1201h
   SS = DOS DS (must be using a DOS internal stack)
   SDA current SFT pointer -> SFT of file to close

Return: CF set on error
   BX???
   CX new reference count of SFT
   ES:DI -> SFT for file

See Also: AX=1106h,AX=1227h,INT 21/AH=3Eh