Multiply-and-accumulate (乘加运算) names the operation that multiplies two numbers and adds the product to a running total — an accumulator. Repeated in a loop, it becomes the workhorse of computation: digital signal processing and neural-network inference are, at heart, long streams of these multiply-then-add steps, which is why hardware designers often fuse the two operations into single MAC units that execute both in one pass [^9a8d57d5-c4c1-5ff4-a785-15650f00fbac@115]. In this channel's captured material, the term surfaces in the live writing session WATCH ME WRITE LIVE WITH CHATGPT VOICE — a roughly two-hour stream in which research, drafting, metaphor-building, and editing blend into one flow while the writer drafts a long history of Codex with ChatGPT Voice [^9a8d57d5-c4c1-5ff4-a785-15650f00fbac@204].