A+ Certification for Dummies describes the Pentium processor as having a 32-bit address bus, 32 bit registers, and a 64 bit data bus. 7 pages later, it describes the Itanium as Intels first 64-bit processor. I checked with an IT associate of mine, and he said the processors size refers to the address bus. PC Guide says it refers to the register size within the CPU. The article went on to say every processor introduced in the last decade, from the earliest 386SX to the latest Pentium II or K6, is a 32 bit processor, based on this definition. I know Im ignorant, but Im trying to understand. There are dozens of numbers on a cpu datasheet. Which one are they talking about when they say Its a 32 bit processor?