Instruction Set Architecture (ISA)
  • is a set of opcodes
  • an ISA specifies the behavior of opcodes running on implementations (i.e. microarchitecture) of that ISA in a fashion that does not depend on the characteristics of that implementation

ISA - How it Relates to Opcodes, Assembly Language,  & Machine Code

see: Instruction

ISA - Classifications

An ISA may be classified in a number of different ways

classification by complexity:

other classifications: