How Software Actually Works

The one-page map · GPT Class · September 2026 · Jensen Loke · jensenloke.github.io

The thesis: agents write code now. The scarce skill is steering — the mental map of where code lives, how it runs, and how it ships. You keep the judgment; the map keeps you in control.
1

Terminal

The machine's honest interface — and the agent's native language. pwd where am I · ls what's here · cd move · cat read · mkdir make. Every file has one address: its path.

2

Files

A file is bytes plus a promise (the extension). Markdown and HTML are plain text with light bones — readable by you, editable by agents. Text is the lingua franca of AI.

3

Apps

The restaurant: frontend asks (dining room) · backend decides (kitchen) · database remembers (pantry). AuthN = who you are (passport). AuthZ = what you may do (keycard). The kitchen always decides.

4

Browser

Type a URL → DNS finds the address → server answers with files → browser renders. HTML = skeleton · CSS = skin · JS = muscle. Client code can display; it can never decide.

5

Deployment

localhost = your machine as a server, safe to break. Vercel ships files (push → live). Supabase hosts the pantry + logins. Docker ships the whole machine, boxed.

6

Git · GitHub · CI/CD

A time machine for folders: add stage · commit snapshot · branch side road · checkout time travel · merge/rebase recombine. PR = propose + human review. Robots check; humans approve.

7

Briefing the agent

AGENTS.md / CLAUDE.md = the orientation, always on. Skills = runbooks, loaded on demand. You write the map in plain text; the agent supplies speed; the files supply consistency.

8

The human

Direction, taste, judgment. Agents hold the wrench — you decide what's worth building. That's the human in the loop.

The round trip, in one breath

Click → request flies out with your keycard → backend checks the keycard → asks the database → the ledger answers → backend cooks → 200 OK returns → browser renders. Whole loop: ~200 milliseconds.

The iceberg

You built the tip: one file, structure, style, logic, a server. Real products add what's underwater — memory (databases, backups), people (accounts, auth, roles), the world (hosting, mobile, scale), trust (tests, security, rollback).