Instruction set architecture
From Computer History Wiki
An instruction set architecture (the term is usually given as the acronym, ISA) is an instruction set design shared across multiple CPU implementations (thereby making object code portable across them, allowing them to share compilers, etc).
Perhaps the most famous example was the first, the IBM System/360 (initially shared across a dozen models in the line, and still in use today), which cemented IBM's place atop the early computer industry. Other examples include:
