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  Interrupt:   21h     Function:   40h
 
  Title:       Write File or Device
 
  See also:    Read File or Device, Set File Pointer, @Write
 
  Description:
 
     Given a valid file handle from a previous open or create
     operation, a buffer address, and a length in bytes, this function
     transfers data from the buffer into the file and then updates the
     file pointer position.
 
     Input                                Output
 
     AH = 40h                             If function successful
     BX = Handle                             Carry flag: clear
     CX = Number of bytes to write           AX = Bytes transferred
     DS:DX = segment:offset of buffer
                                          If function unsuccessful
                                             Carry flag: set
                                             AX = Error code (05h or 06H)
                                             See: ◄Error codes►
                                    -♦-