How does a CD-RW write data to a disc and how is it able to rewrite data to the same disc?

Answer 1

The surface is made of special alloys that are melted by the write laser in the CD-RW drive. These melted areas are read by the laser. When it's time to record over the CD, the laser heats up the alloy and melts the data into a new pattern.

Answer 2

The CD-RW disk has a layer of special dye sandwiched inside the clear plactic disk.

This dye changes it's crystaline properties when heated.

The laser heats the dye to 200 degrees C, which makes it transparent. If it heats it to 600 degrees it becomes opaque.

The digital pulses are written to the disk using a laser that makes transparent patches which can be read by the reading laser as being reflective or not. (1's and 0's)

To re-write data, the disk is first erased by heating to make the dye opaque. The write laser can then record, using pulses that heat to 200 degrees and make clear patches again.

This differs from CD-R, which has a dye that can only be changes permanently once.

Standard CD's have a metal layer which contains physical pits on it, which are punched using a mechanical press. The information is thus permanent.

Answer 3

It 'burns' the data onto the disk's surface.

Although a CD/DVD disk looks smooth, it actually consists of small 'pits', or indents. Each one of these indents represents a logical/digital state of a 1 or a 0. Lots of 1s and 0s in succession result in a data stream, a continuous lie of digital information.

When you burn a CD/DVD you do exactly that, in that you burn 'pits' into the disk's surface.

When a CD is inserted into the CD-ROM drive, a small laser inside the CD-ROM drive is shot onto the surface of the CD. After the laser hits the surface, it will be reflected off the CD's surface. The reflected light is then intercepted by a series of mirrors and sensory devices, which analyzes the light and determines the bit the light represents.

If the light reflected off a huge pit in the CD, then the reflection would not be very bright. (because of scattering. Just as your image, viewed in a worn down mirror, will not be very clear.) Thus, a large pit is interpreted as a zero. Conversely, a smooth area on the CD, called lands, would reflect very well, and thus is interpreted as a one.

Answer 4

Think of this as you would of a LCD TV.

On a normal (write-once) CD/DVD, when the information-keeping layer is excited using the laser, it changes shape and stays that way "for all eternity", retaining the information written.

On -RW (CD/DVD) discs, this layer is constructed using a different material, that can "un-bend" (change back to its original shape) when excited using a laser powered within the "mid-way" range (somewhere between 'read' and 'write'). This way, the entire data layer of a disc can be made to be "flat" again, and thus - it can be "re-shaped" to retain new information.

This flexible material isn't infinitely flexible, though, so an -RW disc only has so many write-cycles before the material's ability to return to the original form is lost - such discs do not last forever. Once this ability is gone, the -RW disc becomes a write-once disc in theory, but by this time even writing on it will become difficult.

Answer 5

Data recording (and erasing) was achieved by heating the magneto-optical layer's material (eg. DyFeCo or less often TbFeCo or GdFeCo) up to its Curie point thus erasing all previous data and then using a magnetic field to write the new data, in a manner essentially identical to Sony's MiniDisc and other magneto-optical formats. Reading of the discs relied on the Kerr effect. This was also the first major flaw of this format: it could only be read in special drives and was physically incompatible with non magneto-optical enabled drives, in a much more radical way than the later CD-RWs.

Answer 6

dont no