What is a 10-key machine?

A 10-key machine is a type of calculator. Specifically, a 10-key is an adding machine used to add numbers together, often used by bookkeepers or accountants.

The 10-key machine got its name from the layout of the keys. Using the numbers 1 to 9 and zero, a person can type the numbers needed into the 10-key machine without looking down. The 10-key machine is useful for adding large lists of numbers together, as when preparing taxes. Many 10-key machines feature a small printer that will print out the numbers and totals as needed. This is also used to check the numbers added for accuracy.