Molly and Owen Pruitt, both 12, use the Raspberry Pi computer to learn the programing process at he Eldersburg Branch of the Carroll County Public Library on Monday.

In early 2012, Eben Upton introduced the Raspberry Pi, a small-board computer aimed at inspiring children raised on tablets to learn computer programing, but adults are buying them.

Raspberry Pi has sold its three millionth unit, a little over two years after the low-cost educational computer now beloved by developers went on sale.… ...