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

8 APPLE II COMPUTER GRAPHICSzeros into something more easily communicated to the human brain, somost modern computers like to speak to people using hex.Hexadecimal, which uses sixteen digits, is used to represent the 256different combinations available with an eight-bit byte. It is conceivable torepresent the value of a byte using a single base 256 digit; however, mostpeople would fi nd it very difficult to remember 256 different digits. There,::fore, in the interest of simplicity, instead of one base 256 digit representingthe value of a byte, two hex digits are used. Why not use decimal which is ,..simpler yet? Do not forget that we are dealing with a group of bits. The tendecimal digits are too many to represent three bits and too few for fourbits, as three bits make for eight combinations, and four bits make forsixteen. The fact that sixteen combinations are available to four bits, andthat hexadecimal uses exactly sixteen digits, is very important. This is thereason that many programmers count like they have sixteen fi ngers!BIT BIT BIT BIT1 2 3 4HEXADECIMAL BINARYDECIMALOFF OFF OFF OFFOFF OFF OFF ON0 0 0 o I o1 0 0 0 101OFF OFF ONOFF2 0 0 1 02OFF OFF ONON3 0 0 1 13OFF ONOFF OFF4 0 1 0 04OFF ONOFF ON5 0 1 0 15OFF ON ON OFFOFF ON ON ON6 0 1 1 07 0 1 1 167ONOFF OFF OFF8I 1 0 0 08ONONOFF OFF ONOFF ON OFF9 1 0 0 1A 1 0 1 o I910ONOFF ONONB 1 0 1 111ONONOFF OFFc 1 1 0 012ONONOFF ONDI 1 1 0 113ONON ON OFFEI 1 1 1 014ONON ON ONF! 1 1 1 I 115Figure 2-2. A binary/hex chart.