in    input    File open for reading: the internal stream buffer supports input operations.
out    output    File open for writing: the internal stream buffer supports output operations.
binary    binary    Operations are performed in binary mode rather than text.
ate    at end    The output position starts at the end of the file.
app    append    All output operations happen at the end of the file, appending to its existing contents.
trunc    truncate    Any contents that existed in the file before it is open are discarded.