Code: The Hidden Language of Computer Hardware and Software, First Edition

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 ...