Bar Code Basics

Most barcodes are "license plates" that identify an item. When read, can be used to look up additional information about the item. Data is read from barcode, sent to a computer, and the computer looks up the price and description of the item from the computer's database.

Read by:

  • scanning a spot of laser light across the entire barcode
  • taking a digital picture of the barcode with a CCD digital camera

Relative widths of both the bars and spaces - code the data stored in the barcode. Reader detects these relative widths and decodes the data. There are about 400 different types of barcodes.

A typical barcode consists of the following:

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  • Quiet Zone – a large space with no printing (sometimes called the “Clear Area”)
  • Start Code – Indicates the start of the barcode
  • Data – The actual data the barcode stores (Check Digit) –A mathematical sum that is used to verify the accuracy of the other elements of the barcode, (not always present)
  • Stop Code – Indicates the stopping point of the barcode
  • Trailing Quiet Zone – Another clear space with no printing

Density or Resolution

  • High Resolution (less than 0.23mm)
  • Medium Resolution (0.23mm to 0.50mm)
  • Low Resolution (greater than 0.50 mm)
  • Rule: For effective scanning with any device, use lowest barcode density possible that will print on a given area on label or page.
  • Code 39 and Code 128 are best choices for most barcode solutions

One Dimentional Barcodes:

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Contain data that is read along the length of the barcode, (does not change its value from the top to the bottom).

May contain numbers only, alpha-numeric data (letters and numbers), or a limited set of alpha-betical characters.

Typically, these are ASCII characters, (which stands for “American Standard Code for Information Interchange”).

Popular one-dimensional symbologies include:

  • Code 39 (“Code 3 of 9”) – available in standard ASCII or full ASCII character sets. Most frequently used symbology in barcode systems today.
  • Code 128 – 128-character ASCII set. Most easily read code with the highest message integrity due to separate message check routines. Usually the best choice when implementing new systems.
  • UPC (“Universal Product Code”) – 12-digit numeric only, contains a unique manufacturer ID number, and product number. Most common barcode for retail product labeling. Typically used for marking small packages, magazines and books. MUST be obtained through the Uniform Code Council!
  • EAN (“European Article Numbering”) – 13-digit, similar to the UPC, becoming more popular with global commerce.
  • Interleaved 2 of 5 – variable length, even-numbered, numeric only, typically used in industrial and master carton labeling.
  • Code 93 – Similar to Code 39, but encodes more characters per inch.
  • Coda bar – Can encode 16 characters in any length message, (capital letters A through D and all numeric digits.

Two-Dimensional Bar Codes (“2D”)

Users want more than a “license plate” for products. Contains more data in the same space, with same ease of readability. A “paper/portable database”

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Two main types of 2D barcodes:

  • Stacked Bar Codes (a.k.a. “multi-row barcodes”)

    • Linear bar codes literally stacked on top of each other.
    • PDF 417 is the best and most common example in use today.
  • Matrix Codes

    • Patterns of cells in square, hexagonal or circular shape
    • Must be read by a camera or CCD (“Charged-Coupled Device”) reader
    • Higher data densities than stacked codes
    • Data Matrix and Maxi Code are good examples

    Many are proprietary and used in narrow industry segments

History of Barcodes

Barcodes are very inexpensive and easy to implement to identify individual products. Barcodes were initially developed in the 1960’s but did not become common use until the 1970’s. Since that time barcodes have become more popular and are on virtually every product found in stores.

Today there are approximately 40-50 symbologies world-wide. Some symbologies, such as ISBN or EAN codes, are tightly governed. The three most common symbologies are: 1D (or linear barcodes), 2D barcodes, and Postal barcodes. Linear barcodes are by far the most common type. These are the barcodes found in grocery stores and are able to be read by the majority of scanners. 2D “stacked” barcodes are basically a bunch of 1D barcodes stacked on top of each other. This type of barcode is frequently found in the parcel delivery trade. The third common symbology is the 2D “Matrix” barcode. Unlike the 1D and the 2D Stacked barcode, the 2D Matrix barcode specifically requires a 2D scanner. The design is blockier than the other barcodes but is able to store more data. If you look at every letter, you will notice these postal barcodes. This type of barcode is primarily for the use of mail sorting machines, however there are certain PDA’s and handhelds that are capable of reading these particular barcodes.

 
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