Code 39: a Really Simple Explanation
You know what a “code 39” is, but you don’t know the name. Seriously. Go to the kitchen, take a cookies tin, do you see the white and black bars above a serie of numbers? Probably you know it as “the barcode”. Ok, that’s the Code 39. I’m sure it is not the first time you see it… in fact it is very familiar, doesn’t it? Ok then, we are going lo learn a little about what it is and waht it is used for.
This barcode was created in 1974 by David Allais and Ray Stevens, and it is used to encode information about the item that is labeled with it. Think for a while: when you are shopping and you go to the cashier, they “pass the barcode” to know the price. But how they know the price if it doesn’t appear at the code? Because the information is encrypted; you can think that it is written in a different language. Machines can understand it and translate the code to know the price.
Let’s talk a little about the structure of a Code 39. It is an alphanumeric barcode, so you can find characters from A to Z, from 0 to 9, and some special characters (., $, /, +, %, and space); usually you will find a * before and after the alphanumerical sequence. Each date character encoded is madeup of 5 bars and 4 spaces (so you have 9 elements for each character); each bar and space can be narrow or wide, and 3 of the 9 elements must be wide (3 of 9! That’s why this code is called like “39″!).
Ok, now you know a little more about this matter. Only don’t expect to find this code in very small items: it has a low data density, so it requires a lot of space to encode data, so only not very small items can be labeled with it.