A long time ago ancient people used fingers to calculate. Of course, this method had certain limitations. The abacus was invented to fill in the gap. Four hundred years ago, Wilhelm Schickard, a German astronomer, invented one of the first calculating machines. Another inventor, Thomas de Colmar, created Arithmometer in 1820. It was the first commercial calculator. We are very lucky, though. We got bash to do calculations. In this project, you will learn to create a simple calculator with bash.