A UPC-A barcode symbol.
A barcode (also bar code) is an optical
machine-readable representation of data. Ori-
ginally, bar codes represented data in the
widths (lines) and the spacings of parallel
lines, and may be referred to as linear or 1D
(1 dimensional) barcodes or symbologies.
They also come in patterns of squares, dots,
hexagons and other geometric patterns with-
in images termed 2D (2 dimensional) matrix
codes or symbologies. Although 2D systems
use symbols other than bars, they are gener-
ally referred to as barcodes as well.
The first use of barcodes was to label rail-
road cars, but they were not commercially
successful until they were used to automate
supermarket checkout systems, a task in
which they have become almost universal.
Their use has spread to many other roles as
well, tasks that are generically referred to as
Auto ID Data Capture (AIDC). Systems such
as RFID are attempting to make inroads in
the AIDC market, but the simplicity, univer-
sality and low cost of barcodes has limited
the role of these other systems. It costs about
US$0.005 to implement a barcode compared
to passive RFID which still costs about
US$0.07 to US$0.30 per tag.
Barcodes can be read by optical scanners
called barcode readers, or scanned from an
image by special software. In Japan, most
mobile phones have built-in scanning soft-
ware for 2D codes, and similar software is
becoming available on smartphone platforms.
In 1932 Wallace Flint started a project at the
Harvard University Graduate School of Busi-
ness Administration to better automate cus-
tomer purchasing. As punch cards were pre-
valent at the time, the system they envi-
sioned used a catalog of items with corres-
ponding punch cards for each one. The cus-
tomer would hand the cards to a clerk who
would load them into a reader. The item
would then be found and retrieved from a
fully automated warehouse. An itemized
bill was automatically produced. In spite of
its promise, punch card systems were ex-
pensive and the country was in the midst