The cpuplot example shows how to use a couple of features that
came new with Qwt 0.4.1/0.4.2

1) Filled curves
2) Display individual axis labels. 
   Here an inverted time axis is shown.
3) Enable/Disable plot items.
4) Draw customized plot items, like a pie chart or a
   curve drawing the area between 2 curves.
5) Draw non Qwt items, by overloading QwtPlot::drawCanvas

The example reads the cpu usage from /proc/stat and /proc/loadavg. 
If they are not available on your OS it displays dummy values.
