To successfully read a barcode, knowledge of the most common barcode system, Numeric Code 39, is a requirement. Numeric Code 39 has four different symbols: narrow white spaces, narrow black spaces, wide white spaces and wide black spaces. Different combinations of these symbols decode into different number values.
Jonathan Washington, a student who developed a method of decoding barcodes, suggests viewing the bars similarly to binary code, where white spaces are zeros and black spaces are ones. Each combination of six symbols creates one actual number in the barcode. A magnifying glass may be required to correctly determine the width of different bars, as they can appear very similar to one another.