01.UPC码的简介和特性
通用产品代码，通常简称UPC码，是美国均匀码理事会制定的一种商品条码。是最早大规模应用的条码，其特性是一种长度固定、连续性的条码，主要在美国和加拿大使用，由于其应用范围广泛，故又被称万用条码。 UPC码仅可用来表示数字，故其字码即为数字0~9。
UPC码共有A、B、C、D、E等五种版本。
UPC码只能用来表示0-9的数字。每7个模组表达一个字符，每个模组有空（白色）与条（黑色）两种状态。
02.应用场景
1、UPC-A
通用商品
2、UPC-B
医药卫生
3、UPC-C
产业部门
4、UPC-D
仓库批发
5、UPC-E
商品短码
UPC条码也有标准版和缩短版两种，标准版由12位数字构成，缩短版由8位数字构成。
标准版的UPC12的编码结构为：系统码(1位) 厂商码(5位) 商品码(5位) 校检码(1位)。
03.编码方式
UPC-A码
用于通用商品，是适用范围最广的一种UPC码。一共有113个模组，每个模组长0.33毫米。左右两个各由9个模组组成的空白。
UPC-A码是定长码，只能表示12位数字。
从左至右，依次是3个模组（101）的起始码、1位的系统码、5位的左侧数据码、5个模组（01010）的中间码、5位的右侧数据码、检查码、3个模组（101）的终止码。
其中，起始码、中间码、终止码的模组长度都要长于数据码。
UPC-B\C\D码
与UPC-A码基本相同。
其中：B码主要用于医药卫生；C码用于产业部门，第二位为系统码，倒数第二位为检查码；D码用于仓库批发，倒数第三位为检查码。
UPC-E码
短码，总长度为8个字码。A码与E码之间数字的对应规则与最后一位检查码有关。
E表示偶码，O表示奇码。UPC-E的奇码与UPC-A的奇码完全相同。
04.举例
从国别码开始自左至右取数，设UPC-A各码代号如下:
N1 N2 N3 N4 N5 N6 N7 N8 N9 N10 N11 C
则检查码之计算步骤如下:
C1 =( N1 N3 N5 N7 N9 N11)*3 C2 = N2 N4 N6 N8 N10
CC = (C1 C2) 取个位数 C (检查码) = 10 - CC (若值为10，则取0)
翻译成英文：
Introduction to UPC Code
01. Introduction and characteristics of UPC code
Universal product code, usually referred to as UPC code, is a commodity bar code formulated by the U.S. Uniform Code Council.
It is the first barcode to be used on a large scale.
Its characteristic is a fixed-length, continuous barcode. It is mainly used in the United States and Canada. Because of its wide range of applications, it is also called a universal barcode.
UPC code can only be used to represent numbers, so its character code set is numbers 0~9.
There are five versions of UPC code: A, B, C, D, and E.
UPC codes can only be used to represent numbers from 0-9. Every 7 modules express a character, and each module has two states: empty (white) and bar (black).
02. Application scenarios
1. UPC-A
General merchandise
2. UPC-B
Medicine & Health
3. UPC-C
Industry sector
4. UPC-D
Warehouse wholesale
5. UPC-E
Product short code
UPC barcodes are also available in standard and shortened versions. The standard version consists of 12 digits and the shortened version consists of 8 digits.
The coding structure of the standard version of UPC12 is: system code (1 digit) manufacturer code (5 digits) product code (5 digits) verification code (1 digit).
03. Coding method
UPC-A code
It is the most widely applicable UPC code for general commodities. There are a total of 113 modules, each of which is 0.33 mm long. The two left and right blanks each consist of 9 modules.
The UPC-A code is a fixed-length code, which can only represent 12 digits.
From left to right, it is the start code of 3 modules (101), the system code of 1 bit, the data code of 5 digits on the left, the middle code of 5 modules (01010), and the data of 5 digits on the right. Code, check code, termination code of 3 modules (101).
Among them, the module length of the start code, intermediate code, and stop code must be longer than the data code.
UPC-B\C\D code
It is basically the same as the UPC-A code.
Among them: B code is mainly used for medicine and health;
C code is used for industrial departments, the second digit is the system code, and the penultimate digit is the check code;
the D code is used for warehouse wholesale, and the third digit is the check code.
UPC-E code
Short code, the total length is 8 characters. The corresponding rule of the number between the A code and the E code is related to the last check code.
E means even code, O means odd code. The odd code of UPC-E is exactly the same as the odd code of UPC-A.
04. Example
Counting from left to right starting from the country code, suppose the codes of UPC-A are as follows:
N1 N2 N3 N4 N5 N6 N7 N8 N9 N10 N11 C
The calculation steps of the check code are as follows:
C1 =( N1 N3 N5 N7 N9 N11)*3 C2 = N2 N4 N6 N8 N10
CC = (C1 C2) take the single digit C (check code) = 10-CC (if the value is 10, take 0)
部分参考资料来源于百度，英语来源于Google翻译。
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