I had never heard this rumour before -- until I attended a free computer class at my local library, and the question was asked, (and answered), by the teacher.
The truth of the matter, as she explained it, is this: B o t h... PCs AND Macs, DO get computer viruses. But, because SO MANY MORE PEOPLE HAVE PCs THAN HAVE MACS, MOST COMPUTER HACKERS WHO CREATE THE VIRUSES DECIDE TO UNLEASH THESE VIRUSES ON PCs, RATHER THAN MACs, BECAUSE THAT WAY, MORE DAMAGE CAN BE DONE TO MORE PEOPLE.
The teacher of our free class earns her living by being a computer programmer. She should know!
