Code 49 was developed by David Allais in 1987 at the Intermec Corporation to fill a need to pack a lot of information into a very small symbol. Code 49 accomplishes this by using a series of bar code symbols stacked one on top of another. Each symbol can have between two and eight rows. Each row consists of a leading quiet zone; a starting pattern; four data words encoding eight characters, with the last character a row check character; a stop pattern; and a trailing quiet zone. Every row encodes the data in exactly 18 bars and 17 spaces, and each row is separated by a one-module high separator bar (row separator).
The code is a continuous, variable-length symbology that can encode the complete ASCII 128-character set. Its structure is actually a cross between UPC and Code 39. Intermec has put the code in the public domain.