A postal bar code is composed of three main components: framing bars, number bars, and checksum bars.

The first bar on the left side and the last bar on the right side of the postal bar code are framing bars for the postal bar code. You can ignore these; they tell the automation equipment when to start and stop reading.

To read a bar code, group the bars into groups of five bars each. Each group of five lines represents a number, as a unique pattern of short bars and long bars.  In the table below, the "|" represents a tall bar and the "," represents a short bar:

   Number   Bar code          Number    Bar code
   ————————-          —————————
     0       ||,,,              5        ,|,|,
     1       ,,,||              6        ,||,,
     2       ,,|,|              7        |,,,|
     3       ,,||,              8        |,,|,
     4       ,|,,|              9        |,|,,

Try it yourself:

start with:

||,|,,|,,|,||,,,,|,|,,,|,|,||,,,,||,|,|,,|,|,,||,,,,,,|||,,|,|

now seperate the bar code into groups of five bars, setting aside the first bar and the last (the framing bars):

Breakdown of Sample Bar Code

+— Framing Bar                                             Framing Bar —+
|                                                                         |
|                                                                         |
v                                                                         v
| |,|,, |,,|, ||,,, ,|,|, ,,|,| ,||,, ,,||, |,|,, |,|,, ||,,, ,,,|| |,,|, |
  ——- ——- ——- ——- ——- ——- ——- ——- ——- ——- ——- ——-
    9     8     0     5     2     6     3     9     9     0     1     8
    ————————————-     —————————-     ———-    —-
             Zip Code                   Zip+4             Last      Check-
                                                          Two       sum
                                                          Digits    Digit
                                                          of
                                                          Street
                                                          Address

                                                           -or-

                                                          Multi-
                                                          Unit
                                                          Digits