And probably too young to have used Atari, Amiga, Acorn, CP/M, MS-DOS,...

No, actually.

Then either you only bought boxed software, or had lots of luck.

I don't know a single person that did not had an AV on those days. Of course in Portugal you could only buy "backups".

I started with an Apple II, then spent a bunch of time on Sun and IBM RT machines; then got to university and a Macintosh and a Next station; then Linux; then back to Macintosh where I've been for the last 15 years.

So mainly UNIX systems.

Apple II does not count, as I don't remember virus for 8 bit systems.

Mac OS < X did had quite a nice list of virus, but it depended on the software source, as I mentioned on my previous post.

EDIT: Just to add my own experience.

Timex 2068 and ZX Spectrum 48+ at home, followed by all Microsoft OSs starting with MS-DOS version 3.3. Also used DR-DOS 5.0.

Friends had ZX-Spectrum +2(A)/+3, Amiga 500 and Atari ST systems, which we used together in computing parties.

Novel Netware, AS/400 and Xenix at the technical school before going to the university.

My first Linux version used the kernel 1.0.9.

The university had Macs LC II available.

But for the 16bit systems used at home, everybody I knew had an AV to check floppy contents before running anything.