You’d think after years of helping my kids with homework I’d possess rocklike certainty about the mere meaning of algorithm, if not about things like how to solve a quadratic equation. Yet it was always one of those words I skipped blithely over, thinking vaguely, “Um, something to do with algebra, I expect.”
Back to school for me! It is related to algebra, but not as obviously as I imagined. An algorithm is basically the step-by-step process whereby a problem is solved; in particular, it describes some types of mathematical formulae (“formulas”? discuss!) that involve variables—those used to calculate mortgage default rates, for example (hmm, they’ve been working overtime lately). It was actually named after a person, who himself was named after a place—the ninth-century Arab mathematician Muhammad ibn Musa, known as al-Kwarizmi from his hometown, the silk-route city of Kwarizm or Khorazm.
(Kwarizm is now named Khiva; it’s in the Uzbekistan desert near the border with Turkmenistan in Central Asia. Unrelatedly, I spent a nervous night there once as a student in the then Soviet Union, in an old madrasah that had been turned into a youth hostel, where my roommate and I had to barricade ourselves into our cell to keep out excitable Uzbek high school students more interested in getting to know Western girls than studying algorithms or anything else.)
Al-Kwarizmi became algorithm; and it turns out that algebra (the word) also owes its existence to Musa, this time from a book he wrote about that subject, Kitab al-Jabr wal-Mugabala, which translates as “rules of reintegration and reduction” (thanks to Roy Blount’s lovely book Alphabet Juice!). Go figure.—TAMARA GLENNY