How Barcodes Work

Barcodes In One Lesson. Barcodes have revolutionized modern life. Discover what happens every time you hear a beep at the checkout.

I was inspired to make this video based upon an explanation of barcodes I found in a great book called Code: The Hidden Language of Computer Hardware and Software http://amzn.to/pR9MwK . I highly recommend it.

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Closed Caption:

this is bar codes in one lesson
bar codes are found in virtually all
products that you see in any store when
a laser from a computer scans a barcode
it's actually scanning through a series
of 95 evenly spaced columns and checking
to see if each one of those columns is
reflecting a lot of laser light or
virtually none computers only understand
ones and zeros so any of the columns
that reflect virtually no light are
considered a one and any of the columns
that reflect a lot of light are
considered 0
probably the reverse of what you might
expect so in this example the computer
begins reading the columns from left to
right the first column reflects
virtually no light so it considers that
a one
the next column reflects a lot of light
so it considers that zero the third
column is like the first
it reflects virtually no light so it
also considers that a 1 the fourth fifth
and six columns all reflect a lot of
light so they are all considered zeros
computer continues reading the columns
all the way across the bar code and
comes up with a number that is ninety
five digits long
full of ones and zeros these ones and
zeros are then grouped into 15 different
sections 12 of these sections are used
for the numbers that you see at the
bottom of the barca the other three are
used as guards these guards let the
computer know where the bar code begins
and ends and also where the six numbers
on each side begin and end this is
important because the numbers on the
left are identified based upon one set
of codes and the numbers on the right
are identified based upon another set of
codes
these codes are different because the
computer needs to know whether it's
reading the bar code from left to right
or whether the bar code is being read
upside down
it figures that out based upon how many
ones there are in the code for each
digit the codes on the Left always have
an odd number of ones and the codes on
the right
always have an even number
ones so if the computer reads an even
number of ones on the left hand side
it knows that the bar code is flipped
upside down and once it reads it
it can just flip the numbers around
before processing them also has an
additional air check all the codes and
the left side begin with a zero and in
with one and all the codes and the right
side begin with the one and in with a
zero so in this case will plug in the
numbers above and you'll see that those
numbers are the exact same as the
numbers below
what do these numbers actually mean the
first number on the left hand side 0
which is outside of the actual bar code
tells us what type of bar code this is 0
is a standard bar code a2 is a weight on
like fruit or meat and three is a
pharmacy item and the five is a coupon
the next set of five numbers tells us
who the manufacturer of the product is
in this case it's the campbell soup
company
the second set of five digits tells us
the product code which in this case is a
10 and three-quarter ounce can of
chicken noodle soup and finally the last
number on the right hand side is called
the modulo check character and this is
another form of error checking when the
computer scans the barcode and processes
the numbers
it needs a final way to know that it red
and processed everything correctly so
performs a calculation and comes up with
the modulo check character
the modulo check character formula is
actually based upon the positions of
each of the numbers at the bottom of the
barcode its first adds up the digits and
the odd number of positions and then it
ends up the digits in the even number of
positions it then multiplies the odd
number of digits by three and adds that
amount to the sum of the even number of
digits so we'll go ahead and plug in the
numbers from our bar code and we come up
with a final total of twenty-three
we then subtract the result of this
formula from the next highest multiple
of 10 to get the modulo check character
so the next highest multiple of 10 after
23 is 30 and 30 - 23 is seven so we know
that we have read the bar code correctly
so now you've learned bar codes in one
lesson