how can u fit 4.7gb of data on a dvd but its still the same size as a 700mb cd?

Question

how can u fit 4.7gb of data on a dvd but its still the same size as a 700mb cd (physically) the extact same size, also how can u fit 700mb data but 800mb audio on a cd?

Answer 1

The data on a CD or DVD is stored in a microscopic code of pits and non-pits, which your CD or DVD drive reads as 1s and 0s (each 1 or 0 is called a bit, 8 bits are one byte, 1024 bytes make one kilobyte, 1024 kilobytes make one megabyte, etc) which it translates into the data that you can access on your computer. On a DVD, each pit or non-pit is much smaller than on a CD, so you can fit more data on one disc.

There is more than one type of CD - some hold 700MB, others hold 800mb. Again, this is because of the size of the individual bits, and thus the density of the data. In fact, some CDs (however rare) hold up to 900MB of data. For more info, see the 'capacity' section of the Wikipedia page below.

Answer 2

Basically there are two physical differences between CD and DVD disc:

The smallest DVD pits are only 0.44 micron in diameter, the equivalent CD pits are nearly twice as large (0.83 microns).
DVD data tracks are only 0.74 micron apart, and once again it is almost double that on a CD (1.6 microns).

So although a DVD is the same size as a CD, its data spiral is over of 6 Miles long, more than twice the length of a CD's data spiral.

To read the smallar pits, a DVD player's readout beam uses a finer focus than a CD player's does.

This amoung with other additional efficiencies of the DVD format capacity of DVDs compared to CDs.

As for the Audio - data question:

When you use a CD as an audio CD, the data isn't quite as robustly stored as when you use a CD as a data CD. Data CDs have more redundancy and error detection/correction than audio CDs, with the trade-off that they hold a lesser amount of user data (about 15% less), this coupled with the fact that 1 MB doesn't always equal 1 MB, there are decimal megabytes, meaning 1,000,000 bytes and also binary-number based megabytes, meaning 2^20 (two to the twentieth power) bytes, or 1,048,576 bytes..

Happy?

Answer 3

It's not much different from a CD except that the laser is more advanced, more precise; more data can be stored in the same surface area.

Likewise data density has been increasing for hard drives over the years - with the result that a 250gb hard drive is no larger than an 800mb one from ten years ago.

Answer 4

About 6 or 7.

Answer 5

The data on a CD and a dvd is stored by burning pits into the cd/dvd. DVD uses a shorter wavelength of laser which allows these pits to be smaller, this means that more can be burned in the same space on a dvd. The newer blueray and HDDVD use even smaller wavelengths of laser (blue light instead of red) allowing even more information in the same space.

DVD can also be dual layer in this two wavelengths of laser are used, one passes through the ower layer reading the top layer the other reads the lower layer.

Answer 6

cds are very much like old time records, except instead of a needle they use lasers. They have little groves of code that goes arround just like the groves on your record players. The closer those groves are to each other the more information you can fit onto a peice of media. Store bought dvds hold even more data, or the computer dual layer ones because they use 2 lasers and 2 platforms of data. Its the same princiables behind the even newer high def and blue ray dvds.

Answer 7

The laser reading/writing the data is of a higher frequency, which means the beam makes/reads a smaller and sharper spot on the disc. Smaller spots means more bits for the same size disc. This is of course for a single layer.

Answer 8

The widths of the tracks on dvds are smaller, allowing more traks on a disc and in some cases have two layers. I suspect the pits are also shorter, even so it does seem like a lot of capacity to create.

Answer 9

Overburn can allow you to exceed the normal limits of capacity of adisk, depends on the burner and software.

The other option is compression... Winrar, lharc and winzip can help there.

Answer 10

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