You write a line of code, and the processor only understands bits. We follow the translation: the two-pass assembler, the compiler phases, linking and loading. Along the way, GCC cuts twelve instructions down to two with -O2, and we see where Python and Java sit between compiling and interpreting.
The same expression costs 5 instructions with three operands, 7 with two, and 11 with an accumulator. We will see the ISA, the contract between hardware and software, instruction formats, the RISC-V R-type, and the seven addressing modes that tell where each operand is.
A hypothetical 12-bit processor with 15 instructions serves as a model for following the complete instruction cycle. We execute LDA and ADD register by register, encode instructions in hexadecimal, and write assembly programs with branches and loops.
