What is the difference between CD and DVD, what are the varieties.

Optical (laser) information storage devices (CDs or DVDs) have become an integral part of our lives. CD and DVD drives are the basis of game consoles, multimedia players, they are equipped with almost all modern personal computers and laptops, and these drives can be found in many cars. Despite this prevalence, few people know how CDs differ from DVDs.

What is an optical disc?

To find out how a CD differs from a DVD, we’ll take a look at the drive design. We will not delve into the scientific jungle, but explain in simple words. The laser disk consists of four layers:

1. A polycarbonate plate is a transparent, colorless plastic, which is the thickest layer, located on top, inscriptions are applied to it, pictures are printed.
2. The working layer is a special dye, it is this layer that is burned by a laser.
3. A thin layer of non-ferrous metal - depending on pricing, gold, silver, aluminum, etc. can be used. It serves to reflect the laser beam.
4. Varnish over metal - the bottom layer protects the information layer.

So, now we find out how the information is written to disk and the recorded is read? The laser beam, moving along a spiral path from the center to the edge of the disk, burns points. The bottom line is that the burned sections of the track do not reflect the laser beam, while untouched, thanks to the metal coating, reflect. That is, a binary code is obtained: the beam is reflected - 1, not reflected - 0. This code is the basis of any digital information.

So what is the difference between CD-R and DVD-R?

The first difference between a CD and a DVD is the size of the laser beam. For DVD-drives it is smaller, respectively, the tracks and burned spots on the DVD-ROM are smaller than the CD. Therefore, on DVD, the standard declared capacity is 4.7 GB, and on CDs - only 700 MB.

The speed of writing and reading is also different. The speed of writing to a CD is faster than writing to a DVD, but the DVD has a higher read speed.

What is the difference between a CD and a DVD?

CDs are usually a bit cheaper than DVDs. Therefore, to record a small amount of information it is faster and more profitable to use the first ones.

In turn, it is easy to distinguish between CD and DVD visually. They differ in the color of the recorded surface: the CD has a pale green reflection, the DVD has dark purple.

DVD discs as a later technology, unlike CDs, have more “useful” varieties.

Varieties of CD and DVD

• Both types of disc can be double-sided. This means that information can be recorded on each side. It turns out twice as much information, but also increases disk storage requirements.
• There are still rewritable discs - CD-RW and DVD-RW. Theoretically, they should withstand 1000 rewriting cycles, but in practice hardly anyone checked.
• DVD discs have a two-layer variety. As the name implies, they have two layers on one side, respectively, and twice as much information on one side. And if both sides are two-layer? That's right, four times as much.
• There are also types that are indicated by the prefixes “+ R” and “-R” (CD + R, DVD + R and CD-R, DVD-R). They differ in that data can be added to “+ R” disks, if there is still free space, respectively, it is impossible to add data to “-R”.

Useful Tips

• Do not skimp and do not buy the cheapest discs. The cheaper the disk, the lower the quality of the materials from which it is made.
• Try not to record at maximum speed. The slower the recording, the less likely it is to record errors.
• Do not store important information on one disk. Make a few copies. The disk may break in the drive, it can easily be scratched, and it is subject to deformation with little heat.

Of course, this article only summarizes the essence of the most complex technology, but we hope that a person who is far from science will be satisfied with the answer to the question of how the CD differs from DVD.