The Secret Life of Bar Codes by Richard Baguley.
From the post:
Some technologies you use every day, but without thinking about them. The bar code is one of these: everything you buy has one of these black and white striped codes on it. We’ve all seen how they are used: the cashier scans the code and the details and price pop up on the screen. The bar code identifies one product of the millions that are on sale at any one time. How does it do that? Let’s find out.
The bar code
The bar code itself is very simple: a series of black and white stripes of varying width. These are scanned by a bar code reader. Here, a rapidly moving laser passes over the code, and a sensor detects the reflection, picking up the alternating pattern of light and dark. A computer translates the differences between the widths of the patterns into numbers. One pattern is translated into a 0, another into a 1, another into a 2 and so on. You don’t have to have a laser to read a bar code, though. There are plenty of apps that can find a bar code in a picture taken with the onboard camera.
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The type of bar code used on products is known as a linear code, because you read it from left to right in a straight line. There are many other types that work differently and that can encode more data, from the QR codes that often contain website addresses to more arcane types such as the Maxicode that UPS uses to store the delivery address on package labels. These aren’t used on products you buy in a store, though, because all the bar code needs to contain for a product sold in the US is a single 12-digit number, called the Universal Product Code (UPC).
The structure of the bar code on things that you buy at the store is based on the UPC-A standard UPC code, This is 12 digits long, but there is a version that shortens this down to seven digits (called the UPC-E standard) by removing some of the data. This makes the bar code smaller, which is useful for smaller products like candy bars or chewing gum.
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Be careful with Baguley’s post. The links I saw while copying are full of tracking BS, which I removed from the quote you see.
Still, a nice treatment of bar codes, one form of identifiers and a common one.
The Barcode Island is a treasure trove of information on bar codes. See also Bar Code 1, which has a link to Magazines on Barcodes.
I can understand and appreciate people learning assembly but magazines on bar codes? Yikes! Different strokes I guess.
Enjoy!