words, short upper and lower bars are assigned weights of 18 & 9, 6 & 3, and 2 & 1, from left to right. Since the first bar has 4 possible values, and the following bars have 3, 2 bars can encode 4×3 = 12 values, while 3 bars can encode 4×3×3 = 36. N characters are simply encoded as the values 0–9. Only the value 9 requires a leading 3. Z characters use the full 36 combinations representable by 3 bars. The values 0–25 encode the letters A–Z, and 26–35 encode the digits 0–9. A characters have a somewhat peculiar encoding. They can also be decoded as three base-3 digits (a leading 3 is never used), with the values 2–26 mostly encoding A–Y. Exceptions are that 0 encodes M, 1 encodes H, 9 encodes Z (rather than H), and code 14 is not used (rather than encoding M). PostBar formats Canada Post uses nine different formats of PostBar codes—three "domestic" barcodes, used on mail within Canada, two "global" codes, used to route mail outside Canada, three "service" codes, used on customer-applied barcodes, and an "internal" code, used for testing, maintenance, and tracking purposes by Canada Post. Each barcode begins and ends with an identical pair of bars, known as "start" and "stop" fields. These are made up of one ascender and one tracker. The Data Content Identifier is always the first character after the start field. Placeholders used to detail each PostBar format below are A, N, Z and B for the character sets described above, * for the start and stop fields, # for a space character (two full-height bars followed by one tracker), and [RS-nn] for the error-correction field, where nn is the number of bars used. Bold Z's indicate DCIs. Domestic See caution at bottom of article regarding use of PostBar codes. DCI's used in domestic barcodes fall within the range of A–L. PostBar.D07: * Z ANANAN [RS-12] * PostBar.D12: * Z ANANAN ZZZZ # [RS-12] * PostBar.D22: * Z ANANAN ZZZZZZZZZZZ [RS-12] * Global DCI's used in global barcodes fall within the range of 1–9. PostBar.G12: * Z NNN ZZZZZZZZ [RS-12] * PostBar.G22: * Z NNN ZZZZZZZZ ZZZZZZZZZZ [RS-12] * Service DCI's used in service barcodes fall within the range of M–U. PostBar.S06: * Z ZZZZZ [RS-12] * PostBar.S11: * Z ZZZZZZZZZZ [RS-12] * PostBar.S21: * Z Z ZZZZZZZZZZZZZZZZZZZ [RS-12] * Internal use DCI's used