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

174 APPLE II COMPUTER GRAPHICSsome of the addresses is that the original language tor the Apple 11, IntegerBASIC, was incapable of handling a number greater than 32767. Thismeant that in order to CALL the 65385 address, you had to refer to itstwo's complement, -1 51 .You can convert any address to its negative equ ivalent by either subtracting65536 from the address (the easy way) or by forming its two'scomplement (the hard way).At this point you have probably learned more than you ever wanted toknow about the hex and binary systems, but you have really just scratchedthe surface. There are several interesting ties between the topics we coveredhere and the fu ndamental algorithms used by a computer. For example,a computer actually figures the sum of two numbers by comparingcorresponding bits and using the logical operations "AND" and " EOR"(described in the text). Pursuing these topics would take us beyond thescope of this text, but that info rmation may be found in a book on Booleanlogic.