> From what I understand, the greatest difference between mainframes and minicomputers (and later, microcomputers), is that mainframes were batch-oriented machines, while minicomputers were interactive-oriented.

Actually, a lot of early interactive computing was done on time-shared mainframes. I learned to program in 1968 when I saw a Teletype machine in our high school math classroom and found out it could dial into a timesharing system where you could write and run programs interactively.

At first we were dialing into a General Electric mainframe, and partway through the year switched to an SDS Sigma 5 at a local Phoenix timesharing company, Transdata. I got my first job there that summer.

The next year I moved to the Bay Area and started working at Tymshare, where we used a variety of mainframes to provide interactive services, along with some minicomputers for network routing. It was the biggest timesharing company of the day, and there were many others.

Timesharing was a big business from the late 1960s through the 1970s. Of course there were many mainframes doing batch processing too, but interactive computing certainly wasn't exclusive to minicomputers or microcomputers.

I heard a lot of Western European governements run on Siemens BS1000/BS2000/BS3000.