Why are barcodes useful?

The graphic structure of a bar code is very simple; it comprises only dark areas and light areas which humans see as the familiar "bars". These bars form a binary system of representation, in other Words the barcode symbol has only two states -- "light" and "dark" --- there is no third state. The graphical simplicity means that it is very easy to place a barcode onto an object. Barcodes can cheaply and easily be printed onto many different materials. Because of this graphical simplicity it is also quite easy to create an electrical gadget that can "see" the barcode. The electronics of the gadget needs to be able to distinguish between "dark" and "light" and that is not technically difficult. Within the software of the gadget the barcode can be represented by a binary numbering system "1" and "0". Consequently it is very easy to interpret that number and convert it to the letters and digits that we humans usually read. Additionally a barcode can suffer quite a lot of damage before it becomes unreadable. The machine reading the barcode only needs to find a straight line (any straight line) between one end of the bar code and the other. That line can be diagonal. If it is possible to draw a line that crosses every bar and does not cross any smudges or gaps then the bar code can, theoretically, be read. There are many different bar code formats in use. Some of them can only represent numbers and some can also represent letters. Some barcode formats also contain extra information that can be used to check that the barcode has been read correctly. This means that if part of the barcode label is missing so that some bars are missing, the barcode read will know that what it is seeing is not a valid barcode. The machine that is reading the barcode can know immediately if it has seen a valid barcode or not. If it cannot see a valid barcode then it can immediately alert the operator of the machine so that they can correct the problem in some other way. These characteristics mean that in many situations a barcode is a very reliable way to transfer information because it is quite easy to avoid false reads and often even damaged barcode labels can still be read very easily. It is hypothetically possible to create a barcode of any length but, in practice, most barcode readers can only read quite short barcodes. Consequently barcodes are used where the information to be transferred is very simple. For example, most of the barcodes used on things that are bought in shops contain only eight, twelve or thirteen digits.