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CODE 11 SYMBOLOGY

 See Also:    Symbology Index

Quick Links:   Background    Check Digit    Encoding    Structure    Encoding Table    Example


CODE 11 BACKGROUND INFORMATION

 Code 11, also known as USD-8, was developed as a high-density numeric-only symbology. It is used primarily in labeling telecommunications equipment. The symbology is discrete and is able to encode the numbers 0 through 9, the dash symbol (-), and start/stop characters. A typical Code 11 bar code is:

Code 11 is not terribly secure in that printing imperfections can quite easily convert one character into another valid character. Data integrity is obtained by using one, or sometimes two, check characters.

COMPUTING THE CHECKSUM DIGIT

Code 11 uses one or two weighted checksum digits. Normally, if the length of the message to encoded is less than 10 characters only one checksum ('C') is used, whereas both 'C' and 'K' are used if the message is 10 characters or longer.

The 'C' checksum digit is calculated by summing the weighted value of each byte in the message, dividing by 11 (modulo 11), and using the remainder as the check digit which is appended to the message. The weight used starts from 1 at the right-most character in the message and increments by 1 as you move to the left, up to 10. If the message contains more than 10 characters, the 11th character is assigned a weight of 1 and the weight again increases by 1 as you continue to move to the lefft.

The 'K' checksum digit is calculated basically the same was as the 'C' checksum digit, but the 'K' checksum includes the 'C' checksum as the right-most character in the message, and the weighting only goes up to 9 before "wrapping around" back to 1.

The steps for calculating the checksum digits, thus, are as follows:

  1. Start at the right-most character in your message and assign that a weight of 1.
  2. Multiply the character value by the weight and add the result to a running checksum total. A dash (-) has a weight of 10.
  3. As you move from right to left through the message, incremenet the weight by one. Thus the second-to-last character has a weight of 2. Repeat step 2 for each character in the message.
  4. Once you've added the weighted value of each character, divide the result by 11. The remainder from this division becomes the 'C' checksum digit. This is appended to your message.
  5. If your message has 10 or more characters, you should also calculcated a second 'K' checksum digit.
  6. Start at the right-most character in your message (which is now the 'C' checksum digit) and assign it a weight of 1.
  7. Multiply the character value by the weight and add the result to a running checksum total. A dash (-) has a weight of 10.
  8. As you move from right to left through the message, increment the weight by one. Thus the second-to-last character (which used to be the last character of the message before you appended the 'C' checksum digit) has a weight of 2. Repeat step 7 for each character in the message.
  9. Once you've added the weighted value of each character, divide the result by 9. The remainder from this division becomes the 'K' checksum digit. This is appeneded to your message after the 'C' checksum digit.
Thus, as an example, if your original message was 123-45, the 'C' checksum digit would be calculated as follows:
    MESSAGE 1 2 3 - 4 5
    Weight 6 5 4 3 2 1
    Weighted Value 6 10 12 30 8 5
Above, we've multiplied each character in the message by its weight depending on its position. We then sum the weighted values 6 + 10 + 12 + 30 + 8 + 5 = 71. We divide this by 11 which gives us 6 with a remainder of 5. Thus our 'C' check digit is 5, and we append this to our message. Our message now becomes 123-455. This message is less than 10 characters, so it would not generally be considered necessary to use a second check digit-but for the sake of example we will calculate it.

    MESSAGE 1 2 3 - 4 5 5
    Weight 7 6 5 4 3 2 1
    Weighted Value 7 12 15 40 12 10 5
Again, we sum the weighted values of 7 + 12 + 15 + 40 + 12 + 10 + 5 = 101. We divide this by 11 and, in this case, we get 9 with a remainder of 2-so our 'K' check digit is 2. We append this to our message and get a final message of 123-4552. These are the characters that are encoded in the bar code.

    NOTE: It is important to remember that the 'C' checksum weighting goes from 1 (right-most) up to 10 and then starts again at 1. The 'K' checksum weighting goes from 1 (right-most) up to only 9 and then starts at 1 again.

ENCODING THE SYMBOL

In the following text, we will discuss the encoding of the bar code by considering that the number "1" represents a "dark" or "bar" section of the bar code whereas a "0" represents a "light" or "space" section of the bar code. Thus the numbers 1101 represents a double-wide bar (11), followed by a single-wide space (0), followed by a single-wide bar (1). This would be printed in the bar code as:

STRUCTURE OF A CODE 11 BARCODE

 A Code 11 Barcode has the following structure:
  1. A start/stop character, encoded from the table below.
  2. Any number of characters encoded from the table below.
  3. An optional (but highly recommended) 'C' check digit calculated as described above and encoded from the table below.
  4. An optional (but recommended for messages with a length greather than 10) 'K' check digit calculated as described above and encoded from the table below.
  5. A start/stop character, encoded from the table below..

CODE 11 ENCODING TABLE

 This table indicates how to encode each digit of a Code 11 bar code. Note that the "Width Encoding" column is expressed as "0" (narrow bar or space) or "1" (wide bar or space) while the "Barcode Encoding" column represents how the bar code will actually be encoded as described above in "Encoding the Symbol."

For example, the character 0 is defined as "00001" by Code 11. This means a "Narrow bar, narrow space, narrow bar, narrow space, wide bar". We convert this to "101011" in the "Barcode Encoding" column which is consistent with the method we've used to express bar code formats in other documents on this site.

    ASCII
    CHARACTER    		WIDTH
    ENCODING    		BARCODE
    ENCODING
    000001101011
    1100011101011
    2010011001011
    3110001100101
    4001011011011
    5101001101101
    6011001001101
    7000111010011
    8100101101001
    910000110101
    - (Dash)00100101101
    Start/Stop001101011001
    NOTE 1: Since the first and last element of every character is always a bar, a narrow space is appended at the end of each character to separate the last bar of a character from the first bar of the character that follows.

    NOTE 2: Code 11 is interesting in that there are always 3 bars and 2 spaces of varying sizes, but the total size (width) of a character varies depending on the character being encoded. The characters 0, 9, and dash only require 6 elements of space whereas the rest require 7.

CODE 11 ENCODING EXAMPLE

We will now code the example we used above, 123-4530. Remember that the original message was just 123-4530/B>, but that we appended two checksum digits in the example above.

    NOTE: The example above was actually 123-4552 but the following example encodes "123-4530".

  1. The START/STOP character: 1011001.
  2. An intercharacter space encoded as 0.
  3. The digit "1": enocded as 1101011.
  4. An intercharacter space encoded as 0.
  5. The digit "2": enocded as 1001011.
  6. An intercharacter space encoded as 0.
  7. The digit "3": enocded as 1100101.
  8. An intercharacter space encoded as 0.
  9. The digit "-": enocded as 101101.
  10. An intercharacter space encoded as 0.
  11. The digit "4": enocded as 1011011.
  12. An intercharacter space encoded as 0.
  13. The digit "5": enocded as 1101101.
  14. An intercharacter space encoded as 0.
  15. The 'C' checksum digit "3": enocded as 1100101.
  16. An intercharacter space encoded as 0.
  17. The 'K' checksum digit "0": enocded as 101011.
  18. An intercharacter space encoded as 0.
  19. The STOP Frame bar: 1011001.
This is shown in the following graphical representation where the bar code has been sectioned-off into areas that reflect each of the 19 components just mentioned. However, the inter-character spacing are not numbered, only the actual characters.

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