A barcode is really a simple idea: give each product a unique number and print it for a scanning device to read. We could simply print the number itself, but this can cause problems. For example, a misprinted eight could look like a three to a computer, while six looks similar to nine if you turn it upside down. What we need is a reliable (可靠的) way of printing numbers so that they can be read accurately (准确地) at high speeds. That’s the problem that barcodes solve.