Code 128

• Code 128 is a very effective, high-density symbology which permits the encoding of alphanumeric data.
• The symbology includes a checksum digit for verification, and the bar code may also be verified character-by-character verifying the parity of each data byte.
• An example of alphanumeric encoding in a single Code 128 bar code is:

Structure of Code 128

• A Code 128 bar code has the following physical structure:
1. Start code, which is the code 103, 104, or 105 from the encoding table below (Start-A, Start-B, Start-C).
2. Each of the data bytes of the message, encoded with the encoding table below.
3. The checksum byte, calculated as described above and encoded using the table below.
4. Stop character of 11000111010.
5. Termination bar of 11.

Encoding the symbol

• The number "1" represents a "dark" or "bar" section of the bar code whereas a "0" represents a "light" or "space" section of the bar code.
• Thus the numbers 1101 represents a double-wide bar (11), followed by a single-wide space (0), followed by a single-wide bar (1).

Check digit calculation

• It is calculated by summing the start code 'value' to the products of each character's 'value' multiplied by its position in the barcode string.
• For example, in the following table, the code 128 variant A checksum value is calculated for the alphanumeric string HI2345678HI:

Code	Value	Position	Value × Position
Start Code A	103	1	103
H	40	1	40
I	41	2	82
3	19	3	57
4	20	4	80
5	21	5	105
6	22	6	132
7	23	7	161
8	24	8	192
H	40	9	360
I	41	10	410
	Sum		1722
	Remainder is (1722 / 103)		74

Code 128 Encoding table

• This table indicates how to encode each digit of a Code 128 bar code.
• Note that it is easiest to think of each character as a value between 0 and 105, inclusive, rather than thinking of them as characters.

Value	Represents in Character set			Encoding	Value	Represents in Character set			Encoding
	A	B	C			A	B	C
00	SP	SP	00	11011001100	53	U	U	53	11011101110
01	!	!	01	11001101100	54	V	V	54	11101011000
02	"	"	02	11001100110	55	W	W	55	11101000110
03	#	#	03	10010011000	56	X	X	56	11100010110
04	$	$	04	10010001100	57	Y	Y	57	11101101000
05	%	%	05	10001001100	58	Z	Z	58	11101100010
06	&	&	06	10011001000	59	[	[	59	11100011010
07	'	'	07	10011000100	60	\	\	60	11101111010
08	(	(	08	10001100100	61	]	]	61	11001000010
09	)	)	09	11001001000	62	^	^	62	11110001010
10	*	*	10	11001000100	63	_	_	63	10100110000
11	+	+	11	11000100100	64	NUL	`	64	10100001100
12	,	,	12	10110011100	65	SOH	a	65	10010110000
13	-	-	13	10011011100	66	STX	b	66	10010000110
14	.	.	14	10011001110	67	ETX	c	67	10000101100
15	/	/	15	10111001100	68	EOT	d	68	10000100110
16	0	0	16	10011101100	69	ENQ	e	69	10110010000
17	1	1	17	10011100110	70	ACK	f	70	10110000100
18	2	2	18	11001110010	71	BEL	g	71	10011010000
19	3	3	19	11001011100	72	BS	h	72	10011000010
20	4	4	20	11001001110	73	HT	i	73	10000110100
21	5	5	21	11011100100	74	LF	j	74	10000110010
22	6	6	22	11001110100	75	VT	k	75	11000010010
23	7	7	23	11101101110	76	FF	l	76	11001010000
24	8	8	24	11101001100	77	CR	m	77	11110111010
25	9	9	25	11100101100	78	SO	n	78	11000010100
26	:	:	26	11100100110	79	SI	o	79	10001111010
27	;	;	27	11101100100	80	DLE	p	80	10100111100
28	<	<	28	11100110100	81	DC1	q	81	10010111100
29	=	=	29	11100110010	82	DC2	r	82	10010011110
30	>	>	30	11011011000	83	DC3	s	83	10111100100
31	?	?	31	11011000110	84	DC4	t	84	10011110100
32	@	@	32	11000110110	85	NAK	u	85	10011110010
33	A	A	33	10100011000	86	SYN	v	86	11110100100
34	B	B	34	10001011000	87	ETB	w	87	11110010100
35	C	C	35	10001000110	88	CAN	x	88	11110010010
36	D	D	36	10110001000	89	EM	y	89	11011011110
37	E	E	37	10001101000	90	SUB	z	90	11011110110
38	F	F	38	10001100010	91	ESC	{	91	11110110110
39	G	G	39	11010001000	92	FS	|	92	10101111000
40	H	H	40	11000101000	93	GS	}	93	10100011110
41	I	I	41	11000100010	94	RS	~	94	10001011110
42	J	J	42	10110111000	95	US	DEL	95	10111101000
43	K	K	43	10110001110	96	FNC3	FNC3	96	10111100010
44	L	L	44	10001101110	97	FNC2	FNC2	97	11110101000
45	M	M	45	10111011000	98	SHIFT	SHIFT	98	11110100010
46	N	N	46	10111000110	99	Code C	Code C	99	10111011110
47	O	O	47	10001110110	100	Code B	FNC4	Code B	10111101110
48	P	P	48	11101110110	101	FNC4	Code A	Code A	11101011110
49	Q	Q	49	11010001110	102	FNC1	FNC1	FNC1	11110101110
50	R	R	50	11000101110	103	START A	START A	START A	11010000100
51	S	S	51	11011101000	104	START B	START B	START B	11010010000
52	T	T	52	11011100010	105	START C	START C	START C	11010011100
						STOP	STOP	STOP	11000111010