How are 1's and 0's stored on CDs and DVDs?
Binary numbers (the 1’s and 0’s) are stored physically onto the surface of CD’s and DVD’s. They are carved into the surface of the disk. A “1” is a pit, groove or bump on the disk. A “0” is no pit.
DVD’s hold more information because they have physically smaller pits and thus can put more pits on the surface of the disk. BluRay disks have even smaller pits and hold even more information.
The information is written in a spiral around the disk from the center outwards.
Some DVD’s are designed to have multiple layers of data and can thus store even more information.
Binary vs Analog data
This scanning electron microscope shows the tiny pits that are curved onto the surface of a CD. The 1’s are where the bumps are. The 0’s are where there are no bumps. This is physically how binary information is stored onto a CD or DVD.
A vinyl music record is analog, not digital. The data (music) is carved onto the surface of the record like the data is carved onto the surface of a CD. The data, though, is carved in a much different way. Rather than the nice, clean pit (1) or no-pit (0) on the CD, the music is etched into the sides of the groove. The sound wave (a continuous analog signal) is carved into the sides of the groove. The needle moves down the groove and the movement of the needle down the groove produces an electrical signal that is turned into sound.