This mechanical analogue computer was invented in the 1600s. The middle section of the ruler could be slid out to work out mathematical functions by reading the numbers on the scale.

The slide rule, also known as a slipstick, is a mechanical device used for performing mathematical calculations. It was widely used by engineers, scientists, and students from the 17th century to the mid-1970s when it was replaced by electronic calculators.

The slide rule consists of two or more scales that slide against each other. Each scale is marked with a logarithmic scale, which allows for multiplication, division, and other mathematical operations. By aligning the scales, the user can read off the result of the operation directly without the need for written calculations.

One of the key advantages of the slide rule is its ability to perform calculations quickly and accurately. With practice, users could perform complex calculations in a fraction of the time it would take with written calculations. In addition, the slide rule is a purely mechanical device, making it reliable and easy to use without the need for batteries or external power sources.

Slide rules were widely used by engineers and scientists for a variety of applications, including calculations for navigation, astronomy, and engineering. They were also commonly used in education, with students learning how to use slide rules as part of their mathematics and science curriculum.

Despite their advantages, slide rules had several limitations. One of the most significant was their accuracy. Because the scales were marked with discrete values, there was a limit to the precision of calculations that could be performed with a slide rule. In addition, slide rules were less versatile than electronic calculators, which could perform a wider range of mathematical operations with greater precision.

Today, slide rules are mostly obsolete, having been replaced by electronic calculators and computers. However, they remain popular with enthusiasts and collectors and are still used in some specialized applications, such as engineering and aviation.

In conclusion, the slide rule was an important tool in the history of mathematics and engineering. Its ability to perform calculations quickly and accurately made it a valuable tool for scientists and engineers for centuries. While it has been largely replaced by electronic calculators, the slide rule remains a testament to the ingenuity of human technology and the power of mathematics.