A short primer on instruction set architecture

by Imen Baili , Menta
EDN (April 13, 2021)

In computer science, an instruction set architecture (ISA) is an abstract model of a computer. It’s also referred to as architecture or computer architecture. Moreover, a central processing unit (CPU), a venue of realization of an ISA, is called an implementation. An ISA specifies the behavior of machine code running on implementations of that ISA in a fashion that does not depend on the microarchitecture providing binary compatibility between implementations.

An ISA can be extended by adding instructions or other capabilities or adding support for larger addresses and data values. An implementation of the extended ISA will still be able to execute machine code for versions of the ISA without those extensions. Machine code using those extensions will only run on the implementations that support those extensions.

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