Elements of the UPC barcode

Barcodes are not really as complicated as they may seem. Another code that was revolutionary was the Morse Code developed by Samuel Morse in 1835.

This code allowed for the transmission of data over a wire with the use of an electric current. A series of dots and dashes were used to represent each letter of the alphabet. The following table shows how the pattern of dots and dashes was used.

Dit 1 unit of time
Dah 3 units of time
Pause between letters 3 units of time
Pause between words 7 uints of time

The letter “S” was represented with dit dit dit, while the letter “O” was represented with dah dah dah. Sometimes dots and dashes are used to represent dits and dahs. With this formula SOS would be rendered:

dit dit dit dah dah dah dit dit dit

Dots and dashes are also an important part of how barcodes function. A white space is used to separate wide and narrow bars. While many of us are familiar with UPC barcodes, there are actually several different forms of barcodes. The term symbology or symbol set is used to describe a particular code. The digits 0-9 are represented in the UPC code, with no letters used. A pattern of both thin and wide bars are used to represent each digit.

Bar codes used in retail
You may wonder how all the information for the products you are purchasing can be contained in that one little barcode on the product. The truth is that it is not all there.

Rather than the products name, description, and price, a barcode actually contains three important pieces of information:

1. The UCC membership information for the product’s manufacturer.
2. The identification number of the product.
3. A check digit to help ensure that the scanner has read the code correctly.

These are the three elements of the UPC barcode. There is a new global standard that is beginning to emerge that is commonly referred to as the Global Trade Item Number or GTIN. This new standard incorporated the UPC.

The GTIN is produced after the barcode is scanned. The store has a products database which is used to lookup the product information. The database record number is the GTIN. All the information about the product, including manufacturer, name, descriptions, color, price, size, etc., has been entered into the database by store personnel. This information is then transmitted back to the cash register so that you have received your total and printed receipt.

While this is a simplification of the whole process, it is a fairly accurate description of how it all works.
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