The Instruction Set Architecture, or ISA, is defined as that part of the processor architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external IO. With the exception of some small deviations and differences in terminology, all Intel and AMD x86 processors share a common ISA. This book focuses on those shared attributes (it does not cover those areas where the two companies have chosen widely divergent solution s which, by definition, fall outside of the ISA specification).