General Caption: Emphemerides, Calculations, Al Khwarizmi (c.780--c.850):

1. Image 1 Caption: An ephemeris page from Corpus Christi College, Oxford or Corpus Christi College, Cambridge, Manuscript 283, circa 12th century. The plural of ephemeris is ephemerides.

   The ephemeris is written in Medieval Latin and uses Roman numerals. The zodiac constellations or zodiac signs listed in the lower right box.

   The image itself is from Otto E. Neugebauer's (1899--1990) The Astronomical Tables of al-Khwarizmi, (1962).

   Al Khwarizmi (c.780--c.850) was a Persian Medieval Islamic mathematician, Medieval Islamic astronomer, and Medieval Islamic geographer.

   Among other things, he wrote the book Al Jabr (c.820) from whose title we derive the word algebra.

   Al Khwarizmi's own name mutated into the modern word algorithm. He is the eponym of algorithm.

   

2. Image 2 Caption: "Calculating-Table by Gregor Reisch (c.1467--1525) in Margarita Philosophica (1503). The woodcut shows Lady Arithmetica instructing an algorist and an abacist (inaccurately represented by Boethius (c.477--524) and Pythagoras (c.570--c.495 BCE)). There was keen competition between the algorism (essentially modern calculations by hand on paper) and abacism from the introduction of the algebra in Europe in the 12th century until its triumph in the 16th century." (Somewhat edited.)

   Algorism ultimately defeated abacism. You can do a very fast simple calculation with an abacus, but there is NO record of the calculation, and so to check the calculation you have to do all the steps over again and probably make a new mistake. And, of course, there is way to go beyond simple calculations. So algorism, with its written record and ability to on to more and more elaborate calculations, had to win.

   To give a comparison case: the abacus was like a calculator; algorism was like a computer.

3. Image 3 Caption: A statue of Al Khwarizmi (c.780--c.850) in his birth place Khiva, Uzbekistan.

Images:

1. Credit/Permission: Anonymous Medieval Islamic astronomer, 12th century (uploaded to Wikipedia by Ruud Koot (AKA User:R Koot), 2006) / Public domain.
   Image link: Wikipedia: File:Corpus Christ College MS 283 (1).png.
   
2. Credit/Permission: Gregor Reisch (c.1467--1525), Anonymous artist, Margarita Philosophica (1503) (uploaded to Wikimedia Commons by User:Rob at Houghton, 2014) / Public domain.
   Image link: Wikimedia Commons: File:Houghton Typ 520.03.736 - Margarita philosophica.jpg.
   
3. Credit/Permission: © Mario Biondi (AKA User:Mario Biondi writer), 2003 / CC BY-SA 4.0.
   Image link: Wikimedia Commons: File:Al Khwarizmi's Monument in Khiva.png.