The invention of barcodes（条形码）is based on a very simple idea.We only need to give each product a specific number and print it. （1）　 　We could simply print the number itself.But this can cause problems.For example，an unclearly printed "seven" could look like a "one" to a computer.It's also true for "three" and "eight". （2）　 　 We need a better way of printing numbers so that they can be read correctly at high speeds.That's the problem barcodes solve.

    Each number in a barcode is shown by seven blocks of the same size. （3）　 　 For example，the number "one" is shown in turn by two white stripes（条），two black stripes，two white stripes，and one black stripe.（4）　 　

    A barcode includes different parts and each one provides a specific meaning.The first part of a barcode tells you the country where the product was made.For example，690—692 is the barcode for China. （5）　 　 .The final part is about the product itself.This is how barcodes work.

A.Then computers can read it directly. B.All information can be shown by barcodes. C.The next part tells you who produced the product. D.And "nine" looks similar to "six" if you turn it upside down. E.Even if you turn it upside down，it isn't similar to any other number. F.These are colored either black or white to show the number zero to nine.