``putStr :: String -> IO ()``
        Writes its ``String`` argument to standard output.

    ``putStrLn :: String -> IO ()``
        Writes its ``String`` argument to standard output, followed by
        a newline character.

    ``print :: Show a => a -> IO ()``
        Writes its argument to standard output, followed by a newline
        character.  You can hand a value of any type to ``print``
        (provided the type is an instance of type class ``Show``).

    ``putChar :: Char -> IO ()``
        Writes its ``Char`` argument to standard output.

    ``writeFile :: FilePath -> String -> IO ()``
        Writes its ``String`` argument to the file named by the
        ``FilePath`` argument. If the file doesn't exist, it will be
        created; if it does exist, it will be overwritten.

    ``appendFile :: FilePath -> String -> IO ()``
        Writes its ``String`` argument to the end of the file named by
        the ``FilePath`` argument. If the file doesn't exist, it will
        be created.