What is an Optical Disc

The information is stored on the compact disc or compact disc (CD) in digital form (binary logic), in a similar way to audio. On a layer of glass and plastic substances, the holes or marks that the reader unit will later detect are engraved with a laser beam. The reader, using optical techniques, with a low-power laser beam, guarantees that it will not suffer any physical damage.

Thanks to the precision of this technique, large amounts of information can be arranged in a very small space. Every bit in these types of disks is called a pit.
One drawback is that on most of these devices, once recorded they cannot be reused for writing. This forces us to build read-only memory devices.

Advantages of using optical discs
€¢ Great compactness: They can store between 60 and 100 times more data than a magnetic disc of the same diameter.
€¢ Direct access: Similar to the access mode of magnetic disks.
€¢ High speed: The access time is very similar to that of magnetic disks and the transfer speed is higher due to the higher recording density.
€¢ Low cost The support and the reader are of very attractive costs compared to the high costs of magnetic hard disks.

CD-R
CD -Rs are the recordable version of CDs . The basis of these media is a substance that changes phase when irradiated with a more powerful laser than that of normal CD players, then appearing for reading as if there were pits analogously to CDs generated from a master.
It is also possible to find substances in which the phase change is reversible, giving rise to recordable and erasable CDs, analogous to hard disks. Currently there are already marketed versions.

WORM
Currently there are other types of optical discs recordable by the user, known as WORM, they are recorded once but can be read multiple times. An evolution of these are known as magnetooptic disks, compatible with the previous ones but that allow erasing the information, which allows rewriting.