What is QR?
QR Code stands for Quick Response Code.
It is a way of representing data in a graphical format using matrix-like structure.
It is made up of black & white squares, called modules, arranged in a grid. The dark modules generally represent a binary one & the light module generally represent a binary zero.
The entire grid (QR code) has 2 main parts:
- Encoding Region: the area where the actual data is encoded
- Function Patters: special patterns that contain meta data & helps with scanning.
QR Codes have 40 different sizes, which are called Version 1, Version 2, & so on up-to Version 40.
Version 1 measures 21 modules x 21 modules,
Version 2 measures 25 modules x 25 modules,
& so on, increasing in steps of 4 modules per side, up to
- Version 40 measuring 177 modules x 177 modules.
We can encode (in the encoding region):
- Numeric data (digits 0–9)
- Alphanumeric data (digits 0–9, Upper case letters A-Z, 9 special characters: space , $ % * + — . / : )
- Byte data
- Kanji characters
The data region also includes data correction codes. It uses reed-solomon error correction, & there are 4 available levels of error correction:
- Low (L) : 7% of data bytes can be restored
- Medium (M) : 15% of data bytes can be restored
- Quartile (Q) : 25% of data bytes can be restored
- High (H) : 30% of data bytes can be restored
To know what goes inside a QR, read the below story.
