Int 21H, AH=28H

1 and higher

RANDOM BLOCK WRITE TO FCB FILE

      AH = 28h
      CX = number of records to write
      DS:DX -> opened FCB (see #01345)
      Disk Transfer Area contains records to be written

AL = status

          00h successful
          01h disk full or file read-only
          02h segment wrap in DTA
      CX = number of records written

write begins at current file position as specified in FCB; the file
        position is updated after writing
      if CX = 0000h on entry, no data is written; instead the file size is
        adjusted to be the same as the file position specified by the random
        record and record size fields of the FCB
      if the data to be written is less than a disk sector, it is copied into
        a DOS disk buffer, to be written out to disk at a later time
      not supported by MS Windows 3.0 DOSX.EXE DOS extender
       

AH=22h,AH=27h,AH=40h,AH=59h/BX=0000h

Text based on Ralf Brown Interrupt List Release 61