Developed in 1974 by David Allais and Raymond Stevens of Interface Mechanisms, Inc., Code 39 was the first barcode to encode both numeric digits and alphanumeric characters. As a result, it remains one of the most popular barcodes in the world.
Code 39 makes it possible to encode digits 0-9, uppercase letters A-Z, along with six symbols: minus, plus, period, dollar sign, slash, and percent. Most barcode readers will generate an error if non-allowed symbols are included in Code 39 elements, meaning this code is considered “self-checking” because a single misinterpreted or incorrect bar will not generate the following valid character.
While Code 39 was groundbreaking for its use of both numbers and letters, it takes significantly more space to encode data in Code 39 than newer codes – such as Code 128 – meaning it’s often not possible to use Code 39 for small-space applications. Because the code can be read by virtually any barcode reader, however, it remains popular worldwide.