williams-et-al-1983-apple-ii-computer-graphics

CHAPTER 2-COMPUTER PHYSIOLOGY 9Taking a Smaller ByteThe next problem is to represent each of the 256 diffe rent values for onebyte using only the sixteen hex digits-the standard (/) through 9, plus theletters A, B, C, D, E, and F; where A stands fo r ten, B for eleven, and soforth through F which stands for fifteen.One byte is represented by two hex digits; each digit represents four ofthe eight bits in that byte. As modern computer whimsy would dictate,each of the two half-bytes is called a nibble (sometimes nybble) . A binarynibble corresponds to a hex digit as shown in Figure 2-2.Suppose that you were looking at a byte with all eight bits turned on.Separated into the two nibbles, it would look like 1111 1111 and wouldcorrespond to hexadecimal FF, since each nibble (1 111) corresponds to F.The binary byte 1