What is This?

Have you ever used the lattice method to multiply? That’s the basis of this tool. It has a set of vertical rods called “bones,” with numbers written on each one. The bones are arranged so that you can multiply or divide numbers by simply adding or subtracting the numbers along the bones. Napier’s Bones helped people do math easily and quickly while on the go.

This is one of the earliest known mechanical calculators. It uses a system of gears and wheels to perform calculations. Unfortunately, Wilhelm Schickard’s prototype was destroyed in a fire, and the design was forgotten for centuries. But it was rediscovered in the 20th century in Schickard’s letters describing the machine. Several replicas have been built based on them!

This calculator uses a “stepped drum” design. Each drum has a series of steps, or teeth, around its edge. Each step corresponds to a different value from 0 to 9. As the drum is turned, it engages these steps as well as levers and gears that allow the machine to perform a wide range of calculations. Later mechanical calculators—even up to the mid-20th century—used variations of this design.

Slide rules were invented in about 1600 but only came into wide use in the 20th century. They are made of wood or plastic and have sliding parts with numbers on them. By moving the sliders, you can solve complex equations. They’re especially helpful for advanced math, like trigonometry. Slide rules were used by scientists, engineers, and students—and helped calculate the paths for rockets to send astronauts to the moon!

In the early 20th century, people began using mechanical calculators called adding machines. The first ones had hundreds of small parts and didn’t use electricity or batteries. Users would input numbers via a large keypad, and the machine would whir and click when the user turned the handle to perform calculations. Mechanical calculators revolutionized offices and businesses. In the 1930s, electric versions of these machines became available.

Engineer Curt Herzstark developed the idea for this hand-cranked device during World War II while he was a prisoner in a concentration camp. He completed his design after the war and started selling his calculator in the early 1950s. About the size of a pepper grinder, it can perform all four operations with speed and accuracy. Users input numbers and turn the crank to complete calculations. Then they observe the mechanical digits move through a small window on the device as it works out the answer.

The company Texas Instruments made microchips for military and industrial devices, but it wanted to make consumer products too. It designed the first handheld electronic calculator. This prototype weighed almost 3 pounds and could add, subtract, multiply, and divide. Calculations were printed onto a thin strip of paper.

With their built-in displays, graphing calculators plot graphs directly on their screens, making it easy to visualize equations and functions. Graphing calculators have become essential tools in high school math and science courses. They bring complex equations and formulas to life!