On this site wherever you see the heron/frog logo a click on it will bring you back here. Microsoft in its infinite wisdom has blocked Flash graphics unless the user gives permission. If things are missing from the page you will see a yellow bar with a message at the top of the screen saying: “To help protect your security Internet explorer has … ”. right click on this bar you will be able to permit the blocked content. Bless them.

© You are welcome to print adapt or reproduce the revision notes, diagrams and animations provided you acknowledge the source as R. Husthwaite, Islay High School.

© I am indebted to PC Advisor’s cover disk of July 2000 (Issue 58) and to Computer Shopper Magazine issue 157 of March 2001 for some of the royalty free clip art provided. The remaining diagrams are my own work.

© Some of the Javascript on this site comes from Alan Gruskoff which he distributes freely. Thank you