1.3.3 (c): descibe the principles of operation of barcode scanners and describe how they are applied to real life scenarios.

A bar code is a series of black and white parallel lines of different thicknesses.

The numbers 0-9 are represented by the series and thicknesses of the black lines. 

Barcodes usually have a left-hand side and right-hand side, separated by guard bars

Each digit is made up of two black lines and two white lines of different thicknesses

The width of each digit is the same, so the speed of scanning is always the same.

The digits on the left hand side start with a white bar and the digits on the right-hand side start with a black bar, which allows it to be scanned in any direction.

The barcode is read by a red laser (LED)

When this happens, the white bars reflect most of the light while the black bars absorb most of the light, allowing the barcode to be read. This reflected light is read by photoelectric cells.

A pattern is then generated and is converted to digital data.

For example,

A barcode digit may be represented as BWBBWBWB physically but as 10110101 digitally.

(B=black W-white)