Gosh that brings back memories. 

Yes, the c64 used the same plug in modems as the vic 20. Talking about modems, I remember getting into ascii codes so I could use the c=64 to access the credit bureau via dial-up like I did with the printing terminal at work. (legally of course). There was one company that made a modem that was proprietary non-standard in a patent sort of way. it was faster than most of the 300 buad modems at the time. You had to use their software or not use the modem. We figured out how the software worked and applied the changes to the modem software everyone used. The Geohotz hack of the time. Never got sued though. Their software was crappy anyway with no up to date file transfer methods. I will never mention the modem company name. I remember writing my own modem software so you could do xmodem file transfers instead of ascii dumps. Eventually wrote my own bbs software.  

No system could read another computer systems disks back then, so moving data was a pain. Not only was the disk formatting different in those days but the way data was represented in a file was also different. The letter "a" might be stored as a 65 on one system and another number on some other system. Once rs232 interfaces came out so computers could talk directly to each other without having to use a modem, we used ascii translators to send files between computers for when people were changing systems so the old files could still be used. In fact, I did quite a bit of that for people to move and use the old eight bit (Apple II, TRS-80, C=64, and etc) data files on the pc.   

Floppy trivia: There was a special gadget that cut slots out of the sides of soft floppies to make them flippies so you could get twice the storage. 

One machine that is not talked about very much that was way ahead of it's time was Datapoint.  Datapoint was an octal not a hex based machine, which made things fun. It was networkable via arcnet. in fact the network addresses had to be configured with jumpers on the cards. That would never work today. The os was multi-user though jobs had to be submitted in batch order. In fact, my first real computer job was a maintenance programmer using databus and rpgII on those systems. They had these bulky 5 and 10 gig removable hard disks that took 10 to 20 minutes to come up to speed in the morning before you could do any work.

