# SunWorld: Security basics, Part 2 - More advice on file attribute bits and modes

Dec 10, 2000, 13:05 (0 Talkback[s])
(Other stories by Mo Budlong)

"While everyone knows that computers are binary, not many people understand the numbering systems that represent the binary numbers stored in computers, or the notational conventions used for displaying this information."

"This may be a teensy bit painful, but I need to cover it to further explain setting file modes. If you understand binary numbering, feel free to skip ahead."

"An odometer in an automobile measures mileage by wheels that rotate through the digits 0 to 9. Each time a wheel completes a revolution from 0 through 9 and back to 0, it trips the wheel to its left up one position. When that wheel reaches 9 and is tripped over to 0, it increments the next wheel to its left."

"Now imagine that each wheel in your odometer only had the digits 0 and 1. The first wheel would increment from 0 to 1 and back to 0 again. As it rotated back to 0, it would trip the wheel to the left over to 1. Wheel 1 would again spin through 1 and back to 0, and this time it would trip wheel 2 over to 0. This would trip wheel 3 over to 1. The following illustrates the sequence of positions for our wheels. The wheel positions are numbered down the left-hand side so that position 0 is 0000, position 1 is 0001, position 2 is 0010, and so on."

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