Do do do do do do are code 39 is also known as USS Code 39?, code 3 / 9?, code 3 of 9?, USD-3?, Alpha39?, type 39?, code 93?. It is a symbology of barcode that can encode the capital letters from A to Z, numbers 0-9 and a handful of special characters like the $ sign. The barcode itself does not contain a check digit, in contrast for example as happens with code 128, but can be considered self-checking by some, on the basis that a wrongly interpreted single bar cannot generate another valid character. Possibly, the most serious disadvantage of code 39 is its low data density, since it requires more space to encode data in code 39 than, for example, in the code 128. This means that very small products may not be labelled with a barcode code 39 as a base.
However, code 39 is still widely used and they can be decoded with almost any barcode reader. One advantage of code 39 is that since there is no need to generate a check digit, it can be easily integrated into existing printing system by adding a barcode font to the system or printer and then print raw in that source data. Code 39 (also known as 3 of 9 barcode) is a length variable, discrete, alphanumeric bar code. Its character set contains 43 significant characters: 0 9, AZ,-,., $, /, +, %, and space. Each character is made up of nine elements: five bars and four spaces. Three of the nine elements are wide (binary value 1), and six elements are narrow (binary value 0). However, the additional common character (**) is used to start and stop delimiters.
The name code 39 is derived from the fact that three of the nine elements that constitute a word in key are elements of width and the remaining six are narrow. Code 39 was developed by Dr. David Allais and Ray Stevens of Intermec in 1974. It was later standardized as ANSI MH 10.8 M-1983 and MIL-STD-1189.