This was the computer you saw in 60s movies about computers; the closest thing to it in a more modern movie was WOPR in WarGames. The big difference was that there were no flashing lights, the one feature Hollywood set designers thought were on all computers.
Most of the memory was from tape drives (the other element of Hollywood computers). There was also something I hadn't known of before: a disk drive. The disks were about three feet across and made of some brown plastic-looking material. I have no idea of their capacity (there was an array of about five of them), but if the held a Meg, I'd be surprised.
Input was by punch cards. We were told never to call them "IBM Cards," since IBM looked askance at that sort of trademark infringement (they probably don't care now). The cards were the size of an old dollar (not the ones in your wallet right now -- an inch or so bigger on each side). You ran them through a card punch -- a typewriter keyboard that took a blank card and punched holes in patterns according to the letter you chose.
I learned some programming on these: BASIC and later FORTRAN. Every card was one line of the program and if you made a typo, you might have to discard the card (though there were tricks to change the mistyped character into something that the card reader would ignore).
After you typed your pile of cards, you put it into a bin. One of the advanced Computer Science students would run it and put the printed out resulted (18" tractor feed paper with pale green strips). If your program ran, you could hand it in. If it didn't (which was likely the case), you'd retype the cards that contained errors and tried again.
Of course, a setup like this was primarily for programming; Word Processing, Spreadsheets, and any function of a modern computer just didn't work. I would also guess that the computer you are using right now has more memory and more storage space that the roomful of equipment back in the early 70s.
But if you wanted to be on the cutting edge back then, this was it.