The encoding of “CSE370”

How would the string CSE370 be represented at the physical level in a barcode?
 

        There are many different formats that barcodes can be encoded into.  Most, however, are very limited in what characters they can encode, and would not be capable of encoding the requested string because of this.  Some, such as Code 3 of 9 and Code 128 are capable of representing most or all possible ANSI characters and could encode the string "CSE370".  The specific question that we will be answering is: How would the string "CSE370" be represented in a barcode using Code 128 Code Set B?

Why Code 128?
        Code 128 is a versatile and commonly used barcode. It has the ability to encode the entire 128 ASCII characters, which include letters, numbers, and symbols. The biggest benefit of Code 128 is its condensed format. Unlike other barcodes like Code 39, Code 128 uses four different bar and space widths. Most other barcodes use only two or three widths. These additional widths let Code 128 use the least amount of space for any code containing six or more characters.
        This report will explore the intricacies of encoding the string “CSE370” by the following step by step process.

The Specifications:
        Code 128 includes 3 character sets defined as Code Set A, Code Set B, and Code Set C. Code A includes all standard alphanumeric keyboard characters as well as special characters. Code B is most commonly used and can encode all standard alphanumeric keyboard characters in upper and lower case in addition to special characters. Code C is used for numeric only encoding, but can double the density of the barcode, thus reducing its size. For the purpose of this report, we will focus on how to encode the string “CSE370” using Code B.
        The structure of every Code 128 barcode consists of the following:

1. Quiet Zone
        The quiet zone, or blank space, must be at least 10 times the width of the smallest unit.

2. Start Character
        The start character varies with each character set to identify what code should be used. Code B’s start character is ”2 1 1 2 1 4”.

3. Encoded Characters
        Each character is represented by three bars and three spaces. The bars and spaces or each character add up to 11 units. The bars and spaces can be up to four units wide. For example, in Code B, the letter “C” is represented by the bar/space pattern “1 3 1 3 2 1”. This is encoded as a bar of width one, followed by a space of width three, followed by another bar of width 1, and so on.

4. Check Digit
        The check digit is calculated by summing the start code value with the product of each character value and its position. This sum is then divided by 103 and the remainder is used as the check digit value. For example, this is how the check digit for the string “CSE370” would be calculated.
 

        643 mod 103 = 21
        Thus, the check digit is the character with the value 21, “5”.

5. Stop Character
        The stop character is the same for all three codes, and is represented by the bar/space configuration “2 3 3 1 1 1 2”. You might notice that this has an extra value and this is because the stop character needs to add an additional bar to the end so that is won’t end with a space.

6. Quiet Zone
        A second quiet zone must be placed at the end of the barcode and must be at least 10 times the width of the smallest unit.

        In addition, every barcode must have a height of at least 0.15 times the length or 0.25 inches, whichever is larger. Following these procedures results in the following barcode.

        This newly formed barcode could then be printed on a physical substrate such as paper or plastic, to be used for some means of identification such as a product identification label, or id badge.  Thus, the string "CSE370" has been represented in a form that, while difficult for a human to read, is easy for a machine to read when scanned by a barcode reader such as those used in your local supermarket.

References
Adams, Russ. “Code 128 Specification Page.” http://www.adams1.com/pub/russadam/128code.html.
(October 28, 2001).

“Code 128 Specification.” http://www.barcodeman.com/info/c128.php3. (October 27, 2001).

“Code 128 / USS Code-128 / UCC128 & EAN128 Barcode FAQ & Tutorial.”
http://www.idautomation.com/code128faq.html. (October 27, 2001).