First things first- the word “barcode” is misspelled! The correct spelling of “barcode” is actually two words- “bar code“.  And it will continue to be misspelled “barcode” everywhere in this blog.

 Why the misspelling? It seems the vast majority of people searching for information on bar codes misspell the word. Hence search engines think the proper spelling of “bar code” is “barcode”- because that’s what everyone is searching for.

 So, what is a barcode? A barcode is a way to display information in a way that machines, rather than humans, can easily read. The simplest barcodes are made up of a series of parallel vertical bars and spaces. These are called linear bar codes. The entire barcode is arranged in a line.

Barcodes must always start with a special character, called a Start Code. Every barcode must end with another special character called a Stop Code. The Start Code tells the barcode scanner to begin reading the barcode and it tells the barcode scanner what kind of barcode is to be read. The Stop Code tells the bar code scanner that it has reached the end of the barcode.

What do I mean by “kind” of barcode? Barcodes are like languages- there are lots of them. Each kind of barcode is designed to do something special. Many barcodes can only represent numbers. Some barcodes let you use portions or the entire ASCII character set. The most common barcode is the one you see on virtually every retail product in stores. It’s called a UPC barcode (Universal Product Code). UPC bar codes must have exactly 12 digits in them. You can not use anything other than numbers in a UPC barcode.

Another kind of barcode is Bar Code 3/9. (Also known as 3 of 9 or 39.)  Bar Code 3/9 lets you use numbers and upper case letters, plus a few special symbols. This type of barcode can be any length, although in practice they probably have at most 30 - 40 characters.

So to summarize, a barcode is a machine readable way of representing information. Some bar codes may show actual text below the barcode itself. This is called a human readable barcode. Some barcodes can only represent numbers, while others can include alphanumeric data. Most barcode scanners can read all linear barcodes. The are lots of different kinds of popular barcodes including: 2/5 Interleaved, 3 of 9, 93, 128, Codabar, EAN, Postnet, UPC, and more.

Further posts will describe the different kinds of bar codes, what you can not do with a bar code, how scanners work, and much more.