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====== Int 21H, AH=3FH ======

===== Version =====

2 and higher

===== Brief =====

"READ" - READ FROM FILE OR DEVICE

===== Family API =====


===== Input =====

        AH = 3Fh
        BX = file handle
        CX = number of bytes to read
        DS:DX -> buffer for data

===== Return =====

 CF clear if successful
            AX = number of bytes actually read (0 if at EOF before call)
        CF set on error
            AX = error code (05h,06h) (see #01680 at AH=59h/BX=0000h)

===== Notes =====

  data is read beginning at current file position, and the file position
          is updated after a successful read
        the returned AX may be smaller than the request in CX if a partial
          read occurred
        if reading from CON, read stops at first CR
        under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
  BUG:    Novell NETX.EXE v3.26 and 3.31 do not set CF if the read fails due to
          a record lock (see AH=5Ch), though it does return AX=0005h; this
          has been documented by Novell
          
===== See also =====

 AH=27h,AH=40h,AH=93h,INT 2F/AX=1108h,INT 2F/AX=1229h

===== Note =====

Text based on [[http://www.cs.cmu.edu/~ralf/files.html|Ralf Brown Interrupt List Release 61]]

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