Classic example of C language - commodity inspection code

          Numbers 013800 15173 5 Appears below the barcode . The first 1 A number indicates the type of goods ( Most goods use o perhaps 7 Express ,2 Indicates the goods to be weighed ,3 It means drugs or health-related goods , and 5 Indicates a gift ). The first group 5 Bits are used to identify the manufacturer (13800 It is the code of Nestle frozen food company in the United States ). The second group 5 Digit numbers are used to identify the product （ Including package size ). The last digit is “ Check bit ”, Its only purpose is to help identify errors in the preceding numbers . If there is an error in barcode scanning , So before 11 Digit numbers may not match the last digit , Supermarket scanners will reject the entire barcode .

         Here's a way to calculate check bits : First of all 1 position 、 The first 3 position 、 The first 5 position 、 The first 7 position 、 The first 9 Position and number 11 Digit number
Add up ; And then put the 2 position 、 The first 4 position 、 The first 6 position 、 The first 8 Position and number 10 Add the digits ; Take a look at my brother's one-time addition of Luo song to , Then add it to the result of the second addition ; Then subtract from the above result 1; The result of subtraction is divided by 10 Take the remainder ; Last use 9
Subtract the remainder from the previous step .

# include <stdio.h>

int main()
{
	int a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11;
	int firstResult = 0, secondResult = 0, thirdResult = 0, fourResult = 0;//fourResult It is the inspection code 

	printf("Please  enter 11 numbers: ");
	scanf("%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d", &a1, &a2, &a3, &a4, &a5, &a6, &a7, &a8, &a9, &a10, &a11);

	firstResult = a1 + a3 + a5 + a7 + a9 + a11;
	secondResult = a2 + a4 + a6 + a8 + a10;
	thirdResult = 3 * firstResult + secondResult;
	fourResult = 9 - (thirdResult - 1) % 10;

	printf("a11 = %d\n", fourResult);

	return 0;
}