abstract interface between hardware and the lowest level software
group of commands that processor can perform, to execute the program instructions
every processor designed is based on 1 specific ISA, which defines the operational capacity of processor in terms of set of commands, that the processor can decode and execute
Intel 8085 ISA, has 246 operation codes, 74 instructions
how ISA is implemented
microarchitecture
processor architecture at the hardware level
actual hardware implementation of the ISA
hardware circuitry of the processor chip that implements 1 particular ISA
