Read only, read/write and WORM tags
Read only tags contain a unique licence plate number which cannot be changed
WORM - Write Once Read Many - enables users to encode tags at the first instance of use, and then the code becomes locked and cannot be changed
Read/write allows for updated or new information to be written to the tag
Read only tags can be the cheapest, because they often require the least amount of memory, but they rely on an infrastrucutre and readily available database to retrieve useful information. Where this is not possible, read/write tags, whcih are more expensive (but do not need large infrastructure) and often used. In many cases these functionalities are combined with segmented memories.