CD - compact disc
DVD - Digital Versatile Disc. stores 7 times more than a CDBlu-Ray - stores 6 times more than a DVDHow It's Made
CD's and similar optical drives like DVDs and Blu-Rays, are made from three very thin layers of plastic and metal. Most of the disc is made from polycarbonate, a tough yet brittle plastic. The middle layer is made of aluminum with a protective plastic layer. The outside of the disc has one surface that's shiny and reflective and the other surface is dull and matte. The matte side is used to to label what's on the disc. To burn information onto a CD, the laser burns a bump aka a "pit" into the disc, a disc can hold 3-5 billion pits. Pits are the zeros in binary code and the lack of a bump is a one. After being lasered with information, the disc is pressed and duplicated for mass production. Then they're covered with a thin layer of aluminum (reflective), the protective polycarbonate layer and the label.
How It's Read
The reflective side is the important side because it's read by a laser. The laser bounces off the reflective side and reads the information on the disc. The information is recorded and then put into binary format, a series of ones and zeros. The laser reads the binaries to receive the information. Since the common CD-ROM drive has been outdated for some years now, people are using DVD multi-drives. It's a DVD drive that reads and burns both DVDs and CDs. BD drives can read Blu-ray and read and write DVDs. There's a more expensive option that will allow one to burn Blu-ray as well. The reason Blu-rays can store so much more than CDs and DVDs is because of the difference in the laser that burns them and the size of the information. Blu-ray is written with a much smaller laser, it's also a blue laser which inspired the name "Blu-ray". DVDs use a red laser that makes light wave with wavelengths 650 nanometers, CDs use an infrared light of 780 nanometers. Since the DVDs wavelengths are shorter, it can hold much more than the CD. In desktop computers, the optical drives attaches to the motherboard.
CD technology was in invented in the late 1960's by James Russell. His goal was to create a sound recording system that sounded just like records and cassette tapes. The first optical sound recording system was patented in 1970 by Russell and he continued to refine it over the years. Im 1982, audio CDs became commercially available in Europe thanks to Sony and Philips corporations. In 1983, they debuted in the Untied States. In the 1990s, CD-ROMs grew in popularity because of their ability to store text, sound, images, animation and video. However since internet has taken over, CD-ROMs are much less popular. This is because they take up too much space on laptops unlike SSDs. The information is then presented on the monitor or through the speakers whether it's optical or audio.