How does a barcode scanner work?

A typical barcode scanner consists of a scanner, a decoder, and a cable that interfaces the decoder to a PC. The scanner scans the barcode symbol by shining a line of light onto the barcode and examining the reflection to capture the bars and spaces of the barcode and then sends this data to the decoder. The decoder translates the bars and spaces into data that a PC can understand and transmits this interpreted data to the PC via a cable in a similar way to how a keyboard sends data to a PC.