how the datas were stored to CDs and read from CDs?

Answer 1

A CD has data written to it via a laser that burns microscopic pits into the surface of the disk. When reading the data, the reading laser either reflects light where there is no burned pit, or scatters light when it encounters a burned pit. There you have your Boolean logic of 1s and 0s.

Answer 2

The blank disc has a pre-groove track onto which the data is written. The pre-groove track, which also contains timing information, ensures that the recorder follows the same spiral path as a conventional CD. Instead of pressing a CD with indentations, a CD-R writes data to a disc by using its lasers to physically "burn" the organic dye. When heated beyond a certain temperature, the area that was "burned" becomes opaque and reflects less light than the areas that have not been "burned". Note that the "burning" process does not produce the conventional indentations (pits). The reflection modulation can be detected by a photo-diode. Upon reading back the stored information, the laser operates at a low enough power not to "burn" the dye and an optical pick-up records the changes in the intensity of the reflected laser radiation when scanning along the groove and over the pits. The change of the intensity of the reflected laser radiation is transformed into an electrical signal, from which the digital information is recovered ("decoded"). The decomposition of the dye in the pit area through the heat of the laser is irreversible (permanent). Therefore, once a section of a CD-R is written, it cannot be erased or rewritten, unlike a CD-RW. A CD-R can be recorded in multiple sessions. A CD recorder can write to a CD-R using several methods including:

1. Disc At Once - the whole CD-R is written in one session with no gaps and the disc is "closed" meaning no more data can be added and the CD-R effectively becomes a standard read-only CD. With no gaps between the tracks the Disc At Once format is useful for "live" audio recordings.
2. Track At Once - data is written to the CD-R one track at a time but the CD is left "open" for further recording at a later stage. It also allows data and audio to reside on the same CD-R.
3. Packet Writing - used to record data to a CD-R in packets allowing extra information to be appended to a disc at a later time or information on the disc can be made "invisible". In this way CD-R can emulate CD-RW however each time information on the disc is altered more data has to be written to the disc. There can be compatibility issues with this format and some CD drives.

A rough estimation of the amount of data on a CD-R can be gained by inspecting the playback side of the disc. A visible variation in the surface can be observed. CD-Rs are written from the center of the disc outwards.

Answer 3

If you're talking about songs, they were stored on CD's in the form of micropits (tiny holes in the readable part of the disk, that creates the rainbow effect). The microscopic pits represent the sound waves of the music. When you put the CD into a player, boombox or computer, a small laser is reflected onto the CD as it spins. If there is no pit, then the laser is reflected back the same way it came out. If there is a pit, the laser's light will be bent (according to the depth and size of the pit) and it will be reflected back in a different way. The reflected rays get detected and the distortion in it is translated into an electrical signal, which is sent to the microphone that translates the electrical signal into a sound wave, therefore creating the music that we hear.

I think the same goes for other types of files stored in CD (except for the microphone and reverting back to sound waves). I think that's where the term CD "burning" came from, when you "burn" pits into the a blank CD.

Answer 4

Digitally, zeros and ones.
0000 = 0
0001 = 1
0010 = 2
0011 = 3
0100 = 4 ...
1000 = 8

Answer 5

They are stored in holes and no-holes, and a laser ray read it.