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AH = 42h AL = origin of move 00h start of file 01h current file position 02h end of file BX = file handle CX:DX = (signed) offset from origin of new file position
Return:
CF clear if successful DX:AX = new file position in bytes from start of file CF set on error AX = error code (01h,06h) (see #01680 at AH=59h/BX=0000h)
Notes: For origins 01h and 02h, the pointer may be positioned before the start of the file; no error is returned in that case (except under Windows NT), but subsequent attempts at I/O will produce errors. If the new position is beyond the current end of file, the file will be extended by the next write (see AH=40h); for FAT32 drives, the file must have been opened with AX=6C00h with the "extended size" flag in order to expand the file beyond 2GB
BUG: Using this method to grow a file from zero bytes to a very large size can corrupt the FAT in some versions of DOS; the file should first be grown from zero to one byte and then to the desired large size
See Also: AH=24h - INT 2F/AX=1228h
Category: DOS Kernel - Int 21h - D
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