A scene with a slide rule

Sometimes I write old, nostalgic articles. The following is what happened when I went to the United States in July 2014, seven years ago, to present my paper at the MIT App Inventor Summit 2014.

Perhaps modern students have never heard or touched what is called a "slide rule", but it was widely used in the world of technical computing. For example, it was actually used in some US national projects, so it's no wonder that some traces of it remain in the United States. The picture below is the elevator entrance of a hotel near MIT (Massachusetts Institute of Technology) where I was staying. I was surprised that a huge slide rule was hung on the top of the elevator door.

A huge slide rule at the entrance of the elevator

Enlarged view

The slide rule was discontinued 40 years ago with the advent of electronic calculators, but I still hold one of them. It was probably produced over 50 years ago. The photo below shows the calculation of "2 x Pi = 6.28" using this slide rule. In addition to multiplication and division, the slide rule can also be used to calculate trigonometric functions, logarithms, square roots, cube roots, etc. by exchanging the middle pard rule.

"2 x Pi = 6.28" on my slide rule

Most of the slide rules made in Japan, including the one shown in the above figure, were made of bamboo. Therefore, there is little deterioration in accuracy due to temperature and humidity fluctuations, and it has been highly evaluated worldwide. The times have advanced. And in the new era, the physical slide rule has disappeared, but as you can see in the picture below, there is a "slide rule software" for Android smartphones! It is useful for understanding the principle of a slide rule.

"2 x Pi = 6.28" in the slide rule app