Popular Mechanics has released an on-line article entitled, "11 Forgotten Media Formats of Yesteryear". The subtitle says, "You remember the floppy drive, but do you remember the Commodore 64 tape drive?" (My answer -- of course, I do!)
They only identify the Datasette with the C64 and not with the other compatible C= 8-bit computers - PET, VIC-20, Plus/4, C128, and CBM II series.
To read about what they say about the Datasette, see