alan.b.pearce@stfc.ac.uk wrote: >> I am helping him privately. > > Well, I suppose that is one way to get the school homework done without r= eading the text book. I think you are right :-). sometimes where there are no proper tutors,=20 students take to asking the world at large :-). Cheers Ravi --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .