Our decimal counting system (base 10, using ten discrete symbols, the numbers zero through nine) is very probably a remnant of counting on one's fingers. If you add your two feet, you can count to twelve, or a dozen. Our abstract, notational system of numbers is tied to the limits of our extremities. But this is not universal. The Aborigines who live in the Torres Strait near Australia use a base two (binary) system, the Sumerians used a base 60, and the Mayans used a base 20. Shao Yung (Chinese philosopher, 1011-1077) proposed a mathematical system based on binary numbers that was a direct influence on Gottfried Wilhelm Leibniz's (German philosopher and mathematician, 1646-1716) use of the binary system. In fact, Leibniz preferred binary to decimal for much of his writing. Some early computers - notably the ENIAC of the mid-1940s—used decimal numbers, stored in complicated devices called decade counters, but their designers quickly realized several advantages to using binary numbers. A binary numbering system, composed of nothing but zeros and ones, is easier to store in an electronic circuit, as either the presence or absence of current in a circuit. More importantly, early computer designers saw that binary numbers shared many properties with the formal logic on which computer programs are based. The EDVAC, completed shortly after ENIAC, was able to store both its data and program in binary digital form.