To read a barcode, you must first determine the barcode type. Barcodes with parallel vertical lines are 1-dimensional. These barcodes are read from left to right. The width of the space and bars relate to specific characters. There are several different character sets, including Code 39 (used by the military), POSTNET (used by the USPS), Codabar, and Interleaved 2 of 5. Each requires a unique method to read.