0 Morty Asked: November 7, 2019In: TechnologyHow do players and computers read CD’s and DVD’s?0I’m just wondering physically how is it possible? Why is it that if I wanna pick one song from the CD the player ‘knows’ where the song I want is?In: Technology ShareFacebook 5 AnswersVoted STobacco400 Added an answer on November 8, 2019 at 4:58 am Answer : this actually blows my mind also You thought CD backside is smooth, but it is not. The fact is they are filled with little bumps. Troff and groves acts like 1 and 0 basically binary. CD reader shines laser into the bumps, the light reflected indicated whether the spot is actually 0 or 1. All of this is happening within nano seconds0Reply Share ShareShare on FacebookShare on TwitterShare on LinkedInShare on WhatsApp rryland Added an answer on November 7, 2019 at 8:33 pm So much wrong in here.A light, laser, is reflected off the disk. This disk has a layer of reflective plastic that has embedded in it a series of pits. Or no pit.When the laser reflects from either a pit or not pit, the concentration of reflected light is different. Think shining flashlight on close object, then an object far away. You can see brightness changes.Anyway, there is a clock that is constantly ticking inside the CD/DVD?whatever reader going0101010101010101010101Each 1 the sensor tells the player what it sees, dark or bright reflection.Now this is when everyone gets it wrong.There is no 0 or 1 represented by pit or not pit. As far as the reader is concerned, all are 0s. Unless, the reflection changes from light to dark or from dark to light. (dark being less light reflected)Fun story time. My friend is an EE, went to Western Digital back in the day to work on this brand new (as in not yet even designed) CD Burner.Mind you the burner was still a few years away.He did not get the job because the HR person said he did not have three years experience with the technology. You know, the technology not yet designed.0Reply Share ShareShare on FacebookShare on TwitterShare on LinkedInShare on WhatsApp stumpdawg Added an answer on November 7, 2019 at 7:04 pm Little tiny reflective/non reflective dots represent 1’s and 0’sThe drives laser shoots at the disc and it being bounced back/not bounces back gets turned into binary0Reply Share ShareShare on FacebookShare on TwitterShare on LinkedInShare on WhatsApp RhynoD Added an answer on November 7, 2019 at 8:13 pm The backside of the label is made of a reflective coating, so that when light is shone through the plastic of the disc it is reflected back out. A laser shines upwards through the disc.In the plastic of the disc there are microscopic dimples or *pits* that change how the laser light is reflected. Specifically, they cause the waves of light to overlap in a way that causes destructive interference, which means no light reaches the detector next to the laser emitter.So either there’s a pit, or a land. Light enters the detector, or it doesn’t. The 1s and 0s of binary are encoded in the pits and lands. It is *not* that a pit or land is a 1 and the other is 0. Instead, a 1 is when the laser detects a *change* from land to pit or vice versa.The laser follows tracks, like the grooves in a record. A chip precisely controls the position of the laser, so the player knows exactly where on the disc the reader is. That means it also knows precisely how fast the disc is turning. It uses that to calculate the clock rate, or how fast 1s and 0s should be happening.DVDs use a more precisely controlled reader and more sensitive reader so the pits can be smaller and closer together, which means more data can be packed onto the disc. The format of the data is also different.Blue ray players use a blue laser, which has a smaller wavelength. That means it can read smaller pits, so they can be even smaller than in DVDs and pack in more data. Blue ray players and HD-DVDs both have multiple layers, too. The laser has a lens to change the focus to ignore or pick up different layers.0Reply Share ShareShare on FacebookShare on TwitterShare on LinkedInShare on WhatsApp rexxar-tc Added an answer on November 7, 2019 at 8:48 pm Nobody answering the question OP asked.A CD, or any optical media is made up of a continuous spiral of 1s and 0s represented as reflective flats, and non reflective pits.At the beginning of the disk is a table of contents of sorts. It tells the system where physically on the media a particular file is. It basically tells the drive that file x starts at sector 423. The drive knows roughly where the laser is physically on the disk, so in order to “seek” to a particular file, it can move the laser and count how many tracks of the spiral it passes over. Once it’s close, it slows down and reads the whole spiral searching for the start of the file. Once the start is found, the data begins to stream from the drive out to the system. From there the file can be played or loaded into memory wholesale and worked on locally.0Reply Share ShareShare on FacebookShare on TwitterShare on LinkedInShare on WhatsAppLeave an answerLeave an answerCancel reply Attachment Select file Browse Featured image Select file Browse What is the capital of UK? ( London )Save my name, email, and website in this browser for the next time I comment.