Answer: IBM 650

In the early years of computing, computers were either one-off affairs designed by (or for) educational and military institutions or, if produced in multiples, they were produced in very low numbers due to their prohibitive costs and construction techniques.

That changed with the 1953 introduction of the IBM 650 computer system. The 650 system was just as big as its formal name (the IBM 650 Magnetic Drum Data-Processing Machine); the base unit had a physical footprint about the size of a deep refrigerator and once you added on the accessory units like the card punch and reader attachments, you had the whole kitchen, so to speak, right there with you.

The size didn’t put anyone off, however, as it was downright compact compared to the much larger computers of the previous decade and the simple calculation machine sold incredibly well. Over the course of its run from 1953 to 1962, the IBM 650 sold almost 2,000 units. These units were used for everything from teaching high school and college students how to program computers to modeling submarine crew performance tables.