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Barcode
A barcode (also bar code) is a machine-readable representation of
information in the widths and spacings of printed parallel lines
(or concentric circles, in at least one symbology). They can be
read by optical scanners called barcode readers or scanned from
an image by special software
History
The idea for the barcode was developed by Norman Joseph Woodland
and Bernard Silver. In 1948 they were graduate students at Drexel
University. They developed the idea after hearing the president
of a food sales company wishing to be able to automate the checkout
process. One of their first ideas was to use Morse code printed
out and extended verticaly, producing narrow and wide bars. Later,
they switched to using a "bulls-eye" type barcode. The
two filed U.S patent # 2,612,994 (click
to see link) on October 20, 1949 for "Classifying Apparatus
and Method". The patent was issued on October 7, 1952.
The first bar code reader was built by Woodland (who was an IBM
employee at the time) and Silver in 1952 and included a 500 watt
light bulb and a photomultiplier vacuum tube made by RCA for movie
sound tracks (which were printed optically on film). This device
was not very practical (the output was simply an oscilloscope, and
the 500 watt bulb nearly caught the paper containing their first
sample barcode on fire), and was not commercially produced. In 1962
they sold the patent to Philco, who later sold it to RCA. The later
development of the laser allowed barcode readers to be made much
more cheaply, and the development of the integrated circuit allowed
the practical decoding of the scanned barcode. Sadly, Silver died
in 1963 at age 38 before anything could come of the patent.
In 1972, a Kroger store in Cincinnati experimented with using a
bull's-eye barcode reader, with help from RCA. Unfortunately, the
bulls-eye barcodes were easy to smudge during printing, and were't
very successful. In the meantime, Woodland at IBM was developping
the linear barcode that was adopted on April 3, 1973 as Universal
Product Code. On June 26, 1974, the first retail product (a pack
of chewing gum) was sold using a barcode reader, at Marsh's supermarket
in Troy, Ohio. (This pack of gum is now in the Smithsonian's Museum
of American History.)
In 1992, Woodland was awarded the National Medal of Technology by
president George H. W. Bush.
Applications
Barcodes (and other machine readable tags like RFID) are used wherever
physical objects need to be tagged with information that is to be
processed by computers. Instead of painstakingly typing long strings
of data into a terminal, the operator only has to display the code
to a barcode reader. It also allows for processing without the help
of human operators in fully automated environments.
The amount of data contained in a barcode varies with the application.
In the simplest case only an identification number is provided which
is used to index into a central database where the complete information
is kept. The EAN-13 and UPC codes commonly found on retail articles
work this way.
In many cases it is more desirable to include the complete information
in the barcode itself without the requirement for an external database.
This led to the development of barcode symbologies that can express
more than decimal digits, ranging from additionally encoding just
the upper case alphabet to the complete ASCII character set and
beyond. The drive to encode ever more information in combination
with the space requirements of simple barcodes led to the development
of matrix codes which are often also named 2D barcodes, although
most do not consist of bars but rather a grid of square cells. Stacked
barcodes are a compromise between true 2D barcodes and linear codes,
and are formed by taking a traditional linear symbology and placing
it in an envelope that allows multiple rows.
Symbologies
The mapping between messages and barcodes is called a symbology.
The specification of a symbology includes the encoding of the single
digits/characters of the message as well as the start and stop markers
into bars and space, the size of the quiet zone required to be before
and after the barcode as well as the computation of a checksum.
Symbologies can be classified mainly by two
properties:
- Continuous vs. discrete: Characters in continuous symbologies
abut, with one character ending with a space and the next beginning
with a bar, or vice versa. Characters in discrete symbologies
begin and end with bars; the intercharacter space is ignored,
as long as it is not wide enough to look like the code ends.
- Two-width vs. many-width: Bars and spaces in two-width symbologies
are wide or narrow; how wide a wide bar is exactly has no significance
as long as the symbology requirements for wide bars are adhered
to (usually two to three times as wide than a narrow bar). Bars
and spaces in many-width symbologies are all multiples of a basic
width called the module; most such codes use four widths of 1,
2, 3 and 4 modules.
Types of barcodes
Linear barcodes
| Symbology |
Cont/Disc |
Two/Many |
Usage |
| Plessey |
Continuous |
Two |
Catalogs, store shelves, inventory |
| UPC |
Continuous |
Many |
USA retail |
| EAN-UCC |
|
|
Worldwide retail |
| Codabar |
Discrete |
Two |
Libraries, blood banks, airbills |
| Interleaved 2 of 5 |
Continuous |
Two |
Wholesale |
| Code 39 |
Discrete |
Two |
Various |
| Code 93 |
Continuous |
Many |
Various |
| Code 128 |
Continuous |
Many |
Various |
| Code 11 |
Discrete |
Two |
Telephones |
| POSTNET |
Continuous |
Tall/short |
Post office |
|
Stacked barcodes
| Symbology |
Notes |
| Codablock |
Stacked 1D barcodes. |
| Code 16K |
Based on 1D Code 128. |
| Code 49 |
Stacked 1D barcodes from
Intermec Corp. |
| PDF417 |
The most common 2D barcode.
Public domain. |
| Micro PDF417 |
|
|
2-D barcode
| Symbology |
Notes |
| 3-DI |
Developed by Lynn Ltd. |
| ArrayTag |
From ArrayTech Systems. |
| Aztec Code |
Public domain. |
| Small Aztec Code |
|
| Bullseye |
This was the barcode
tested in a Kroger store in Cincinnati. It used concentric
bars. |
| Code 1 |
Public domain. |
| CP Code |
From CP Tron, Inc. |
| Data Glyphs |
From Xerox PARC. |
| Data Matrix |
From RVSI Acuity CiMatrix. Now Public Domain |
| Datastrip Code |
From Datastrip, Inc. |
| Dot Code A |
|
| HueCode |
From Robot Design Associates. Uses greyscale
or colour. |
| INTACTA.CODE |
From INTACTA Technologies, Inc. |
| MaxiCode |
Used by United Parcel Service. |
| MiniCode |
From Omniplanar, Inc. |
| QR Code |
From Nippondenso ID Systems. Public domain. |
| SmartCode |
From InfoImaging Technologies. |
| Snowflake Code |
From Marconi Data Systems, Inc. |
| SpotCode |
Circular code from High Energy Magic Ltd. |
| SuperCode |
Public domain. |
| UltraCode |
Black-and-white & colour versions. Public
domain. |
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