What is a Bar Code?
A bar code is simply a set of symbols used to represent alphanumeric information. Basically, instead of seeing the number "1", or the letter "A", you would see a series of bars, both fat and thin, used to represent that number.

So, why replace the alphanumeric characters with a bar code in the first place, you might ask. Humans can easily determine that a strange combination of lines and curves and dots are put together to form a letter or number, but computers aren't as quick in deciphering such information. Even though Optical Character Recognition has come a long way in recent years, it's much quicker and much more accurate for a mechanical device to decode  series of black and white lines than it is to read human text.

A number of bar code standards have been developed and refined over the years into accepted languages called symbologies. We would use different symbologies for different application in the same way that we would use a bold or italic font to emphasize a particular line of text in a report. Different symbologies, or "bar code fonts" are used for different applications. By having standardized symbologies, we ensure that when you print a bar code, I will be able to scan and decode it with my equipment and you will be able to scan and decode my bar codes-as long as we both use the same code and are within the specifications dictated by the barcode standards.

Bar code symbologies come in two basic varieties. They can be either linear or two dimensional in their configuration. A linear bar code symbology consists of a single row of dark lines and white spaces of varying but specified width and height, as indicated by the example below.

Similarly, a 2-Dimensional symbology can be configured into a stacked or matrix format. Two-dimensional bar codes are special rectangular codes that 'stack' information in a manner allowing for more information storage in a smaller amount of space.

The amount of data that can be encoded in a linear barcode symbology is more limited than that of a 2-D bar code symbology. A one inch 2-D matrix symbology, for example, can encode thousands of characters of data, whereas a comparable linear bar code would have to be several feet long to hold the same amount of information.

Bar Code Quality and Printing
Generally Speaking:
The chances for a simple, reliable read, as well as a first read rate, increase with a higher print quality. The risk of substitution errors with a different bar-space sequence decreases as well.

The following examples, with elements enlarged 20-50 times, show that the quality of printed bar codes (through an offset or a matrix printer) is much poorer than by using photographic methods. This means that bar code reading systems must be able to read in spite of imperfections in print. In order to check print quality and print tolerances, there are devices in the market that can judge the readability of the code. More complex devices can even measure the width of each bar and display the scan profile.