What is an algorithm?

An algorithm is like a recipe: it takes inputs, follows clearly defined steps and produces an output. The word comes from the name of the 9th-century Persian mathematician Muhammad ibn Musa al-Khwarizmi, whose works introduced systematic arithmetic methods to Europe. Ancient examples include the Euclidean algorithm for finding the greatest common divisor, described around 300 BC. In computing, algorithms sort data, find the fastest route on a map, compress files and rank search results. Today the word is often used for the recommendation systems behind social media feeds, which decide what content each user sees.