The first barcode was developed in 1948 by two graduate students at Drexel Institute of Technology, Bernard Silver and Norman Joseph Woodland. They filed for a U.S. patent in October 1949 and it was granted in 1952. Its implementation was made possible through the work of Raymond Alexander and Frank Stietz, two engineers with Sylvania, as a result of their work on a system to identify railroad cars (who were also granted a patent). It was not until 1966 that barcodes were put to commercial use and they were not commercially successful until the 1980s. [1] While traditionally barcode encoding schemes represented only numbers, newer symbologies add new characters such as the uppercase alphabet to the complete ASCII character set and beyond. The drive to encode more information in combination with the space requirements of simple barcodes led to the development of matrix codes (a type of 2D barcode), which do not consist of bars but rather a grid of square cells. Stacked barcodes are a compromise between true 2D barcodes and linear codes, and are formed by taking a traditional linear symbology and placing it in an envelope that allows multiple rows.