In our brief history of computing in Chapter 1, we mentioned the abacus as an early computing device. More specifically, the abacus is a device that uses positional notation to represent a decimal number. The beads in any one column represent the digit in that column. All columns combined represent a complete number. The beads above the middle bar represent units of 5 and the beads below the bar each represent 1. Beads pushed away from the middle bar do not contribute to the number. The following diagram shows the number 27,091 represented on an abacus: The user performs calculations by moving the beads in specific ways to reflect the basic arithmetic opera-tions of addition, subtraction, multiplication, and divi-sion. Though ancient, the abacus is still used today in many Asian cultures. In stores, a checkout clerk might use an abacus instead of an electronic cash register. Although lacking some of the advantages of electronic devices, the abacus is more than sufficient for the kinds
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This note was uploaded on 01/13/2011 for the course CSE 1550 taught by Professor Marianakant during the Fall '10 term at York University.