you should know that Apple has it's own type of "virus", called a Ghost, which screws your system files and stops apps from working.
There are actually 3 'viruses' for mac's but they only targed PPC chip mac's and are pretty much dead. the ghost 'virus' is covered by the built in firewall in the OS. So either your teacher is very stupid by not keeping the software upto date, or your just telling porky's
yea with windows the most easy scripts is a virus
even an 10 year old kid can make a virus for windows.
but i bet there more viruses for mac then 3