How does a QR code work?

The idea of transmitting information using graphic elements that will be recognized automatically appeared in the middle of the 20th century. Philadelphia grocery merchants were desperate for a convenient tracking and accounting system, and they approached Drexel University with a request to develop one.

The creator of the first barcode, Norman Woodland was inspired by Morse code: he explained that he simply expanded the dots and dashes, turning them into wide and narrow strokes. To read them, it was supposed to use optical sound recording technology. Due to technical difficulties, the implementation of the idea took twenty years: the first item with a barcode (a pack of Wrigley chewing gum) was sold in 1974.

Barcodes quickly found application in industry: they were convenient for marking parts and accessories. But this was not enough for all companies. In Japan's Denso Wave, a car parts manufacturer, workers asked management to develop a more efficient system, and in 1994 it appeared as a matrix (two-dimensional) code. It was named Quick Response Code - a quick response code or QR code.

Benefits of a QR Code:

• Allows you to encode more information than linear barcodes;
• Easily recognized by scanning equipment;
• Can be read even if damaged.

Although Denso has registered the term “QR Code” as a trademark, the system itself is open source and there is no license fee to use the codes. All this has allowed QR codes to take over the world.

All QR codes have something in common: a white frame, three identical black squares in the corners (each in a double frame), another black square (smaller, but also framed), stripes of black and white modules. This is the technical part of the code that allows the camera to pinpoint its location and estimate the size of the modules. The code also contains information necessary for its correct recognition: about the mask, correction level and version. All the remaining fields can be used to convey information.

Each QR code can contain:

• 7089 digits;
• 4296 letters and numbers in Latin;
• 1817 hieroglyphs;
• 2953 bytes of binary code (that is, about 2953 Cyrillic letters in windows
• 1251 encoding or 1450 in utf-8).

The creation of a QR code takes place in several stages:

1. Information is encoded in one of the ways (digital, alphanumeric, byte or kanji), turning into a stream of bits - a sequence of zeros and ones;
2. Service information is generated that determines the version of the code and encoding;
3. The resulting streams are split into blocks;
4. Correction bytes are added to each block, depending on the selected code version;
5. Two blocks (original data and corrections) are combined into one stream to form a data sequence.
6. The data is entered in the code field. To do this, the space remaining after the introduction of the mandatory elements is divided into two-module columns. They are filled with a "snake", zero - white module, one - black.