QR Codes, what are they?

Do you know what a QR code is?

It's one of those 2-D barcodes you see cropping up all over the place. The QR stands for Quick Response. You may have seen this one around school...

A QR code can be a number of things.

• It can be a link to a website (like the one on the right).
• It could simply be a piece of text with some information on.
• It can write a SMS (text) on your phone, with the number to send it to already there
• It can be a mobile phone contact, ready to save.
• An iTunes link, or an Android Marketplace link.

Go and have a look at http://www.qrstuff.com/ for easy ways to create your own.

There are three main ways to read QR codes like the one above...

1. On an iPhone. Go to the App store, and search for a QR reader.
   
2. On an Android. Again, go to the App market, and search for a QR reader.
3. Using a PC and webcam. You will need software to read the codes. I recommend QuickMark (which is also available for iPhone / Android).
   

Look out; here comes the maths bit.

A QR code is a 2-dimensional array. Each pixel is either black or white. QR codes like the one above are 32 pixels by 32 pixels. How many different QR codes do you think there can be?

Mathematicians would try to make it simpler to work out (at first). What about a 4 x 4 QR code? How many do you think there would be. If you want to practice colouring some there is a blank grid here...

Be careful - even with the smaller grid there are a huge number of possible codes - think systematically.