General-purpose registers are used to store data close to
the processor, where the processor can access the information even more quickly than when the value is in
memory. Different computers have different numbers of registers, and the size of the registers will be congruent
with the word size of the computer (16-bit, 32-bit, etc.).
The number of registers, and the nature of the special-purpose registers, comprise an important part of the
computer architecture. In the case of the Intel x86 architecture, there are four 32-bit general-purpose registers
(EAX, EBX, ECX, and EDX), and four 32-bit registers devoted to address calculations and storage (ESP, EBP,
ESI, and EDI). One could say much more about registers in the Intel x86 architecture, but they are now too
complex to describe completely, as the architecture has been cleverly expanded while maintaining complete
compatibility with earlier designs.
INSTRUCTION SET
The quintessential definition of a computer??™s architecture is its ???instruction set.??? The actual list of things
the computer hardware can accomplish is the machine??™s instruction set. Given the wide variety of computer
applications, and the sophistication of many applications, it can be surprising to learn how limited and primitive
the instruction set of a computer is.
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