C++ Basic Output		    Bob Walton, 7/16/96


Values can be output in C++ by statements such as:

    int x = ...;
    foo y = ...;
    cout << "x = " << x << ", y = " << y << endl;

In order to make the above work, one must:

    #include <iostream.h>

The outputting is done by the operator <<.  `cout' is
the standard output stream, and is of type `ostream'.

If

    struct foo
    {
	int value;
    };

is the definition of `foo', then a possible definition
for the << operator to output a `foo' value is:

  ostream & operator >> ( ostream & s, foo const & v )
      { return s << "foo (" << v.i << ")"; }

Here `s' is an `output stream', which might be `cout'.
A representation of `v' is output to this `ostream',
and the ostream is returned as the value of the <<
operator so calls to the << operator can be concatenated
as in `cout << x << y'.  Note that the ostream is passed
by reference (&).

The standard data types print what one would expect.
Number types print without any surrounding spaces if
output by << to an output stream that has not been
specially modified to do otherwise.  Such modifications
can be made by `output manipulators', which will not be
described here.

There is a special output manipulator to flush an output
stream so its contents are sent to the output device,
and not stuck in internal buffers.  This is the `flush'
output manipulator, for which a typical use is:

    cout << "Input a number: " << flush;

The `endl' manipulator may be used similarly: it outputs
a new line and then does a flush.  Thus lines are often
ended with `<< endl'.  One can end lines with "\n" or
'\n' if one does not care about flushing internal
buffers to the output devices.  Also, reading `cin'
generally causes the `cout' to be flushed before input
occurs.