This question is from the option topic "The software developers view of the hardware". The details required to answer the question are found in chapter 10 p338-344 of my text. If you're not using my text (I'm Sam Davis), then you should, however, chap 10 is one of the chapters on our web site
www.pedc.com.au so I guess you could nick it!
Nice site this and if you've got any questions by all means contact me.
Sam