Chapter 15. Bytes and Hex

The two improved adding machines of the last chapter illustrate clearly the concept of data paths. Throughout the circuitry, 8-bit values move from one component to another. Eight-bit values are inputs to the adders, latches, and data selectors, and also outputs from these units. Eight-bit values are also defined by switches and displayed by lightbulbs. The data path in these circuits is thus said to be 8 bits wide. But why 8 bits? Why not 6 or 7 or 9 or 10?

The simple answer is that these improved adding machines were based on the original adding machine in Chapter 12, which worked with 8-bit values. But there's really no reason why it had to be built that way. Eight bits just seemed at the time to be a convenient amount—a ...

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