Int 21 Fn 15  - DOS 1+ - Sequential Write To Fcb File                      [D]

   AH = 15h
   DS:DX -> opened FCB (see AH=0Fh)
   [DTA] = record to write

Return: AL = status
       00h successful
       01h disk full
       02h segment wrap in DTA

Notes: writes a record of the size specified in the FCB beginning at the
     current file position, then updates the current block and current
     record fields in the FCB
   if less than a full sector is written, the data is placed in a DOS
     buffer to be written out at a later time
   not supported by MS Windows 3.0 DOSX.EXE DOS extender

See Also: AH=0Fh,AH=14h,AH=1Ah,AH=40h,INT 2F/AX=1109h