Barcode-Glossary

Origin

The Code PDF417, developed by Symbol Technologies Inc., USA in 1989, is a so-called stacked, two-dimensional barcode. By way of the standardization activities carried out by ANSI and AIM, the code became – among other codes - industrial standard. In the ASCII-Mode, the PDF is able to present the entire, complete ASCII-range of characters and – additionally – up to 772 extended special characters.

Example of a PDF417 symbol:

PDF417

Symbology Terms

The term PDF417 means:

  • PDF --> Portable Data File
  • 4 --> 4 bars and 4 spaces per code word
  • 17 --> 17 modules per code word

The characters are stored in so-called code words.

Ranges of Application & Businesses/Trades

  • Shipping and transportation business
  • On passports
  • Warehousing and distribution

Classification

  • Two-dimensional symbology, also called „2 D-Code“.
  • This symbology is at times also referred to as stacked or multiple-row symbology.
  • A multiple-width code is also called modular symbology.

Advantages / Strong Points

  • Advantages / Strong Points
  • A very compact and customizable code. Owing to the easily adaptable width, height and information density, the barcode symbol can be flexibly adjusted to the available space.
  • The code is readable with nearly all commonly used reading devices as long as the relevant decoder is individually adjusted.
  • Owing to the high information density of the PDF417, extensive data volumes can be stored in a symbol, or medium-sized data volumes can be stored in a very small data space.
  • By making use of the error correction level, even abraded and damaged barcode symbols can be read.

Disadvantages / Weak Points

  • The stacked structure of the barcode symbol requires a specific modus operandi when reading barcodes.

Codeable Character Set

  • 0 1 2 3 4 5 6 7 8 9
  • A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
  • a b c d e f g h i j k l m n o p q r s t u v w x y z
  • SP ! “ # $ % & ’ ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~
  • NUL SOH STX ETX EOT ENQ ACK BEL BS HAT LF VT FF CR SO SI DLE DC1 DC2 DC3 DC4 NAK SYN ETB CAN EM SUB ESC FS GS RS US
  • And binary characters from 0 to 255.

Symbol Properties

  • Start / stop characters
    Each barcode has a start character on the left side and an optional stop character on the right side.
  • Code Words
    In the barcode PDF417, single bars and spaces do not encode any data. Data are stored in "code words". A "code word" is a sequence of 4 bars and 4 spaces that represent altogether 17 module widths. 1 module is the smallest possible width of a bar or a space. The figure 417 in PDF417 refers to the structure of the "code words" (see the previous text under "Symbology Term"). Die "code words" are placed between the start characters (left) and the stop characters (right). The zone between the start and the stop character comprises several different types of "code words": data code words, control code words and row indicators. All "code words" are placed according to strictly defined rules.
  • Row indicator code words
    One row indicator is situated next to each start and stop character. This indicator contains information about the row, the number of columns and the "error correction level" used.
  • Data code word region
    Information data are at first encoded as figures. These figures are transformed into "code words" that are represented in form of bars and spaces. The data code words are placed between the left and the right row indicator.
  • Rows
    When taking a closer look, a PDF417 symbol appears to be consisting of a row of stacked 1-D Barcodes. Indeed, a PDF417 consists of a row of lines. A PDF417 symbol can consist of 3 to 90 lines. As the number of lines is not pre-defined, a PDF417 can take many different shapes, according to the number lines and columns that are defined.
  • Columns
    A PDF417 symbol consists of a row of columns that are also referred to as data columns. The number of columns can lie between 3 and 30. The columns contain encoded information data as well as check digits and correction characters. Within one PDF417 symbol, up to 928 "code words" can be encoded.

Check Digits & Data Security

PDF417 offers error correction options. Owing to the error correction procedure, reading devices are able to read a soiled, stained or damaged barcode. How much of the original barcode can get damaged depends on the number of check and correction code words used. The user can chose between 9 different security levels (error correction levels). In case of security level 0, a PDF417 symbol cannot be corrected but a defect can be localized. In case of security levels between 1 and 8, defects can be corrected. The higher the security level, the more defects can be corrected. Of course, the symbol grows with the security level. The growing number of correction code words diminishes the capacity for information data.

Symbol Example

Starting from the left, a symbol consists of:

  • A leading quiet zone.
  • A start character (running across the entire symbol height).
  • A left line indicator per code line.
  • Up to 30 code words in up to 90 code lines, containing information data.
  • A right line indicator per code line.
  • An (optional) stop character (running across the entire symbol height).
  • A closing quiet zone