These patterns can also be pressed into the plastic layer based on the etchings of another disc. This may be done in mass production efforts after a master disc has first been created to serve as a template.
Computer files stored in this manner can be made up of several billion etchings or more, depending on the size of the file. Because the bumps made in the plastic are so small, optical discs can still hold large volumes of data. In order to accommodate the large file sizes, etchings are wound around the optical disc in a spiral shaped pattern.
As we can see in the picture below, each information spiral begins at the inner edge of the disc. This allows the data files stored on the disc to be accessed directly, without needing to open irrelevant files.
Picture courtesy of HowStuffWorks. The next layer surrounding the plastic layer is reflective aluminum. The data encoded in the plastic layer is eventually read and interpreted as the disc reflects backs the laser beam.
The detector, on the other hand, easily distinguishes 0s and 1s as the disc reflects the light differently from etched and unetched parts of the surface. This layer protects the optical disc from common traumas that might damage its memory. A typical optical disc reader used in everyday personal computers.
Picture courtesy of ExplainThatStuff. While the individual structure of an optical drive can vary, most are functionally very similar to the disc players commonly found in laptops, such as the one shown above.
In these players, optical discs can be detachably secured to a mount that allows the disc to rotate quickly and freely. In order to read the disc and access the data stored there, the drive uses a laser to shine a light on the bumps and gaps etched into its plastic layer. While the basic technology for optical storage has existed since the late 20th century, substantial improvements are under way to this popular platform.
One key advance in optical storage was the invention of Blu-ray discs. This is why these discs cannot be erased. So these discs can be erased. They often come in a floppy-disc style case to protect the disc. The discs are much higher quality than normal DVD-RWs and can reliably store data for up to 30 years. This means that they are often used for video and data back-up and archiving.
Sorry to ask you this, but Menu Home Read Me First! Data and Information What is a System? What is a Computer? Bits and Bytes 1. User Interfaces Types of Computer 2. Computer Networks What is a Network? Why Use Networks? Why Not Use Networks? It is a very cheap and reliable way to store large amounts of data.
Memory can be direct or sequential. Direct is memory also known as random access. This means that any location in storage can be jumped to at any moment, eg on a direct device such as a DVD, you can jump straight to a chapter. On a sequential device, records are stored one by one in an ordered sequence, eg on a film reel or video tape you have to wind through to find the point you want - you cannot jump straight to it.
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