You know you’re old when kids open Windows Explorer and ask, “why do the drive letters start from C?” and you explain that, in the old days, DOS assigned drive letters A and B to the floppy disk drives; then they ask, “what’s DOS? What’s a floppy disk?” You know your are old when all you want to do is to stay at home sleeping with the backrest pillow for bed.
If they’re lucky they won’t ask about the capacity of a diskette; they might just die ROFL when you tell them that it’s around 1MB.
But if you don’t know what ROFL means then you’re really really old.