QR codes: patterns that carry information — Technology, 7–10 years
A QR code turns information into a pattern of dark and light squares. A camera can read that pattern quickly and turn it into a link, a short message or another piece of data.
The idea
The squares in a QR code are not a picture chosen for decoration. Their positions represent tiny pieces of information, while special corner marks help the camera find the code and its direction. Extra information can help the reader notice and correct some small errors.
Why it was needed
Typing a long address or product number on a small phone is slow and easy to get wrong. QR codes were designed so a machine could capture lots of characters in one quick scan, even when the code was printed on a label or poster. They solve the copying problem, not the problem of deciding whether the destination is safe.
Worked example
A museum prints a QR code for its ticket page. The page address is converted into data, and that data becomes a pattern of squares with corner markers. You open the camera, point it at the whole code, and the phone reads the pattern, rebuilds the address and offers to open it.
The common trap
It is easy to think a QR code is automatically trustworthy because it looks official and technical. But anyone can print one and make it lead somewhere unexpected. Treat the code as an address: check the preview, the website name and the situation before opening it or entering information.
Where it is used
QR codes appear on museum labels, food packaging, event tickets, menus and some payment systems. They connect a physical object to digital information without making you type a long address. Their usefulness depends on a camera, suitable software and a destination that still exists.
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