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## Appendix A. Binary and Hexadecimal

You learned the fundamentals of arithmetic so long ago, it is hard to imagine what it would be like without that knowledge. When you look at the number 145 you instantly see “one hundred and forty-five” without much reflection.

Understanding binary and hexadecimal requires that you re-examine the number 145 and see it not as a number, but as a code for a number.

Start small: Examine the relationship between the number three and “3.” The numeral 3 is a squiggle on a piece of paper; the number three is an idea. The numeral is used to represent the number.

The distinction can be made clear by realizing that three, 3, |||, III, and *** all can be used to represent the same idea of three.

In base 10 (decimal) math ...

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