Code 39 barcode encoding

[Code] [39] is an alpha-numeric [barcode], that is also known under the names [LOGMARS] ([Logistics] [Application|Applications] of [Automated] [Marking] and [Reading] [Symbol|Symbols]), Code 3 of 9 or the 3 of 9 Code¹.
It is commonly used for various barcoding [label|labels], such as name [badge|badges], [inventory] and [industrial application|industrial applications]. The code is easy to use and is designed for [character] self-checking. The [asterisk] character is used as the [start] and [stop] character and therefore should not be included in the [sequence] to be [encode|encoded].

LOGMARS

[LOGMARS] is an [application] of Code 39 used by the [United States Department of Defense]. It is defined under [Military Standard] [MIL-STD-1189B].

How to read Code 3 of 9

Code 3 of 9 is readable by [human|humans], if you know how. A number of things to remember are:

The code is in [binary] [format], see the [code table] below for the last step of [conversion].
[Stripe] or no stripe (further referred to as [black] and [white]) has no relation to the character at that position being a [0] or a [1], the [width] of the stripe determines this ([narrow] = 0, [broad] = 1).
The stripes are alternated, i.e. first stripe is black, then white, then black, then white, then black, [etcetera].
Each character consists of 9 [binary digit|binary digits], and therefore also of 9 consecutive stripes.
The code starts and ends with an [asterisk] ("[*]"), which has code 010010100.

So here's the deal:

Start at left.
First stripe is black (duh!).
Width is narrow (or at least it should be), so jot down a 0.
Next stripe is white and wide, so 1.
Next black and narrow, 0.
[Repeat] this until you're done with all the stripes.
If correct, you should come up with a number of digits divisible by 9, so group them together in groups of 9.
The first and last group of digits should be 010010100 (="*", start and stop character).
Next, look up the groups of binary digits in the [table] below and you've got your [original] sequence of [digit|digits] and characters.

Lookup table for characters

011000100 = space
010101000 = $
000101010 = %
010010100 = * (Start/Stop)
010001010 = +
010000101 = |
110000100 = .
010100010 = /
000110100 = 0
100100001 = 1
001100001 = 2
101100000 = 3
000110001 = 4
100110000 = 5
001110000 = 6
000100101 = 7
100100100 = 8
001100100 = 9
100001001 = A
001001001 = B
101001000 = C
000011001 = D
100011000 = E
001011000 = F
000001101 = G
100001100 = H
001001100 = I
000011100 = J
100000011 = K
001000011 = L
101000010 = M
000010011 = N
100010010 = O
001010010 = P
000000111 = Q
100000110 = R
001000110 = S
000010110 = T
110000001 = U
011000001 = V
111000000 = W
010010001 = X
110010000 = Y
011010000 = Z

Sources:
http://www.idautomation.com/code39faq.html
The barcode [generator] [demonstration] [program] by J.I. Mercanti:

	barcode39.mdb

	Barcode Generator for Code 3 of 9, Code 39, and Mil-spec Logmars.

	version 2.0 (updated for MsAccess 97)

	(c) 1993 - 1999 James Isle Mercanti, Cocoa Beach, FL  32931.  USA

	Permission granted for [public use] and [royalty-free] [distribution].
	No mention of [source] or [credits] is required. All rights reserved.

	email: jamesmercanti@hotmail.com

¹ Makes you think of another [seven of nine|# of 9], huh? Exactly where the three comes from I haven't yet figured out. Perhaps it's three parts (start character, encoded sequence, end character)?
OK, thanks to [spazm] for this: it's called three of nine, because of the nine binary digits, three are 1's (wide stripe) and the rest are 0's (narrow stripe)

[May 5, 2001]

three of nine (thing)