🔧 Lab 06 — Touch Real Data

Time: about 60 minutes. Tools: a web browser, a phone with photos on it, paper and a pen. Nothing to install, nothing to sign up for.

Four exercises. Each one puts your hands on real data — the same formats and structures the lesson described. Do them in order if you can, but each stands alone.

Exercise 1: Make and open a CSV (15 min)

You’ll create a real CSV file about five friends, then open it as plain text to prove there’s no magic inside.

Route A — with a plain text editor (works on any computer):

  1. Open the simplest text editor you have: Notepad on Windows, TextEdit on Mac (in TextEdit, use the menu to switch the document to “plain text” mode first).

  2. Type a heading line, then one line per friend — exactly this shape, with your own real friends:

    name,city,favorite_food
Amara,Lagos,jollof rice
Ben,Toronto,pancakes
Chloe,Manchester,dumplings
Deepa,Pune,dosa
Elias,Berlin,pretzels
  3. Save the file as friends.csv (if the editor insists on .txt, save it, then rename the ending to .csv).
  4. Now double-click the file. On most computers it opens in a spreadsheet program — your typed commas have become columns, your lines have become rows.

Route B — with Google Sheets (works on a phone or any browser):

  1. Go to sheets.google.com and start a blank spreadsheet (this route does need a Google account — if you’d rather not, use Route A).
  2. Type the same table: headings in the first row (name, city, favorite_food), one friend per row below.
  3. Find the Download option in the File menu and choose Comma-separated values (.csv).
  4. Now open the downloaded file with a plain text editor (not a spreadsheet app — on a phone, a notes or file-viewer app that shows raw text).

✅ What you should see (both routes): the same information wearing two outfits. In a spreadsheet: a tidy table. In a text editor: bare lines with commas. Nothing hidden, nothing binary — a CSV is text, and now you’ve verified it personally. You have created structured data: every row, same slots. That’s the tax form, not the shoebox.

Exercise 2: Look at live JSON from a real public service (15 min)

Real services all over the internet hand out data as JSON to anyone who asks — no password needed. You’re going to ask, using nothing but your browser’s address bar.

  1. In your browser, try this address (type or paste it exactly):

    https://api.open-meteo.com/v1/forecast?latitude=52.52&longitude=13.41&current_weather=true

    This asks Open-Meteo, a free public weather service, for the current weather in Berlin (latitude 52.52, longitude 13.41).

  2. Look at what comes back: curly braces, "labels": values, nested boxes — live JSON, generated for you a second ago. Find the temperature in it. Find the wind speed.
  3. Make it yours: replace the latitude and longitude in the address with your own city’s (search the web for “latitude longitude” plus your city name), and reload.
  4. Also try worldtimeapi.org — its front page explains a simple pattern like worldtimeapi.org/api/timezone/Europe/London for asking the current time anywhere, again returned as JSON.

⚠️ Watch out: public services occasionally move or retire their addresses. If either one fails, nothing is wrong with you or your browser — search the web for “free public JSON API”, pick any example that needs no key or sign-up, and paste its address. The goal isn’t these two services; it’s seeing real JSON arrive in your browser.

✅ What you should see: a wall of { "curly": "braces" } that, after this module, you can actually read. Notice it’s the exact shape from the lesson: keys, values, boxes inside boxes. Your weather app does precisely this every time you open it — it fetches JSON like yours and paints a sun icon over it.

Exercise 3: Inspect a photo’s metadata on your phone (10 min)

Time to read the label on the box — on your own photos.

  1. Open your phone’s photo app and pick a photo you took yourself, outdoors, months or years ago.
  2. Find the details view:
    • iPhone: open the photo and swipe up on it, or tap the ⓘ info button.
    • Android: open the photo, tap the three-dot menu, and choose Details or Info (or swipe up, on some models).
  3. Read what your phone wrote down without asking you: the exact date and time, the phone model, camera settings — and, if location was on, a map of where you stood.
  4. Now the privacy check: think of the last photo you sent or posted. Did you know it might carry a map pin? Explore your camera settings — every phone has a switch for whether photos record location, and most messaging apps strip location metadata when sending, but not all services do.

✅ What you should see: more than you expected. That’s the point. The photo is data; everything on the details screen is metadata — and it wrote itself. You don’t need to turn anything off today; you need to know it’s there, and now you do.

Exercise 4: Sketch the table behind your favorite app (15 min)

Paper and pen. You’re going to do real data design — the same first step professional engineers do on whiteboards.

  1. Pick an app you use daily. WhatsApp works beautifully; Instagram or your banking app also work.
  2. Ask: what is the main “thing” this app stores? For WhatsApp: a message. One row per message.

  3. Draw a table. Write column headings: what facts must the app record about each message for the app to work? Start with these and add your own:

    | sender | recipient | text | time_sent | read_yet? | |—|—|—|—|—|

  4. Fill in three rows with made-up-but-realistic messages between you and a friend.
  5. Now interrogate your design — each question you can answer from the table is a feature you’ve explained:
    • Which column makes the ✓✓ “seen” ticks possible?
    • How would the app show messages in order? (Which column? This is why time_sent matters.)
    • What column would you add to support group chats? Voice notes? Deleting a message “for everyone”?
  6. Stretch goal: sketch a second table your app must also have (WhatsApp: a contacts or groups table) and draw an arrow showing how a column in one table points at rows in the other. If you do this, you have independently reinvented the core idea of relational databases — Module 12 will feel like coming home.

✅ What you should see: a paper table that explains real app behavior. The moment “read_yet?” clicks as the ✓✓ column, something permanent happens: apps stop being magic surfaces and become tables with good outfits. That lens never turns off — you’ll catch yourself sketching the table behind every new app you meet.

Done?

You’ve now written, fetched, inspected, and designed real data — four formats, zero installs. Take the quiz, skim the resources, and then it’s on to Part 3: Module 07 — From Idea to App.