The earliest, and still the cheapest, barcode scanners are built from a fixed light and a single photosensor that is manually “scrubbed” across the barcode.
Barcode scanners can be classified into three categories based on their connection to the computer. The older type is the RS-232 barcode scanner. This type requires special programming for transferring the input data to the application program.
“Keyboard interface scanners” connect to a computer using a PS/2 or AT keyboard–compatible adaptor cable. The barcode’s data is sent to the computer as if it had been typed on the keyboard.
Like the keyboard interface scanner, USB scanners are easy to install and do not need custom code for transferring input data to the application program.
The fist product to have a bar code was Wrigleys gum.
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