The pits and flats that are the coded sound on a compact disc can be clearly seen, 930 times their actual size, on the magnified picture of a disc with its outer plastic covering drawn back.
A laser beam scans the pits and flats. It converts them to On and Off flashes of light.
The light flashes are converted to a coded string of pulses of electric current. This represents the binary digits (top right) for the numerical values that convert the electric current to a continuous wave.
Each of the numerical values is a measurement of current strength at points along the wave. It was sampled during the recording 44,100 times each second, so accurately represents the original sounds. The system of binary coding provides 65,535 possible sound levels for each of the sample measurements.
When the varying electric current is amplified and fed to a speaker, it is changed to sound waves that reproduce the recording.