Crucially, the processor only understands —raw binary patterns (e.g., 10011010 00110011... ). A processor’s instruction set architecture (ISA) is the contract between hardware and software: it lists every binary operation code (opcode) the CPU can directly perform. The Intel x86, ARM, and RISC-V are different ISAs. A processor is, in essence, a very fast, very stupid slave that follows binary orders without question.
| Layer | Abstraction | Physical / Logical Unit | Example | |-------|-------------|-------------------------|---------| | | Problem solving | Software | c = a + b; | | Compiler | Translation | Compiler executable | Assembly ADD r3, r1, r2 | | ISA | Hardware/Software boundary | Instruction Set | 0b0001000000010101 | | Processor | Microarchitecture | Register file, ALU, CU | Fetch-Decode-Execute | | Digital Circuit | Logic functions | Adder, MUX, Flip-flop | Ripple-carry adder | | Logic Gate | Boolean algebra | NAND, NOR, AND, OR | CMOS NAND gate | | Transistor | Switch | MOSFET | Voltage-controlled switch | The Intel x86, ARM, and RISC-V are different ISAs
