A bar code that stores information in two-dimensional spaces in the horizontal and vertical directions is called a 2-dimensional bar code.
Like a one-dimensional bar code, two-dimensional bar code also has many different encoding methods, or code system. As for the coding principles of these codes, they can be generally divided into the following three types.
1. Linearly stacked QR code
Based on the principle of one-dimensional bar code encoding, multiple one-dimensional codes are stacked in the vertical direction. Typical code system such as: Code 16K, Code 49.PDF417 and so on.
2. Matrix QR code
It is encoded in a rectangular space by different distributions of black and white pixels in the matrix. Typical code systems such as: Aztec, Maxi Code, QR Code, Data Matrix, etc.
3. Postal code
Coded by different lengths of the bar, mainly used for mail encoding, such as: Postnet, BPO 4-State.
In many kinds of two-dimensional barcodes, commonly used code systems include: Data Matrix, Maxi Code, Aztec, QR Code, Vericode, PDF417, Ultracode, Code 49, Code 16K, etc.
* The Data Matrix is mainly used for the identification of small parts in the electronics industry. For example, this code is printed on the back of an Intel Pentium processor.
* Maxi Code was developed by U.S. United Parcel Service (UPS) for the sorting and tracking of packages.
* Aztec was launched by the American company Welch Allyn and can hold up to 3832 digits or 3067 alpha characters or 1914 bytes of data.