For faster burning speeds, you need more advanced laser-control systems and a faster connection between the computer and the burner. You also need a blank disc that is designed to record information at this speed.
In addition to this wide compatibility , CD-Rs are relatively inexpensive. The main drawback of the format is that you can't reuse the discs. Once you've burned in the digital pattern, it can't be erased and re-written. In the mid '90s, electronics manufacturers introduced a new CD format that addressed this problem. CD-R discs hold a lot of data, work with most CD players and are fairly inexpensive. But unlike tapes , floppy disks and many other data-storage mediums, you cannot re-record on CD-R disc once you've filled it up.
CD-RW discs have taken the idea of writable CDs a step further, building in an erase function so you can record over old data you don't need anymore. These discs are based on phase-change technology. In CD-RW discs, the phase-change element is a chemical compound of silver, antimony, tellurium and indium. As with any physical material, you can change this compound's form by heating it to certain temperatures. When the compound is heated above its melting temperature around degrees Celsius , it becomes a liquid; at its crystallization temperature around degrees Celsius , it turns into a solid.
In a CD-RW disc, the reflecting lands and non-reflecting bumps of a conventional CD are represented by phase shifts in a special compound. When the compound is in a crystalline state, it is translucent, so light can shine through to the metal layer above and reflect back to the laser assembly. When the compound is melted into an amorphous state, it becomes opaque, making the area non-reflective. In phase-change compounds , these shifts in form can be "locked into place": They persist even after the material cools down again.
If you heat the compound in CD-RW discs to the melting temperature and let it cool rapidly, it will remain in a fluid, amorphous state, even though it is below the crystallization temperature. In order to crystallize the compound, you have to keep it at the crystallization temperature for a certain length of time so that it turns into a solid before it cools down again.
In the compound used in CD-RW discs, the crystalline form is translucent while the amorphous fluid form will absorb most light. On a new, blank CD, all of the material in the writable area is in the crystalline form, so light will shine through this layer to the reflective metal above and bounce back to the light sensor.
To encode information on the disc, the CD burner uses its write laser , which is powerful enough to heat the compound to its melting temperature. These "melted" spots serve the same purpose as the bumps on a conventional CD and the opaque spots on a CD-R: They block the "read" laser so it won't reflect off the metal layer. Each non-reflective area indicates a 0 in the digital code.
Every spot that remains crystalline is still reflective , indicating a 1. As with CD-Rs, the read laser does not have enough power to change the state of the material in the recording layer -- it's a lot weaker than the write laser.
The erase laser falls somewhere in between: While it isn't strong enough to melt the material, it does have the necessary intensity to heat the material to the crystallization point. By holding the material at this temperature, the erase laser restores the compound to its crystalline state, effectively erasing the encoded 0.
This clears the disc so new data can be encoded. Some newer drives and players, including all CD-RW writers, can adjust the read laser to work with different CD formats. For the most part, they are used as back-up storage devices for computer files. As we've seen, the reflective and non-reflective patterns on a CD are incredibly small, and they are burned and read very quickly with a speeding laser beam.
In this system, the chances of a data error are fairly high. In the next section, we'll look at some of the ways that CD burners compensate for various encoding problems. In the previous sections, we looked at the basic idea of CD and CD-burner technology. Using precise lasers or metal molds, you can mark a pattern of more-reflective areas and less-reflective areas that represent a sequence of 1s and 0s. The system is so basic that you can encode just about any sort of digital information. There is no inherent limitation on what kind of mark pattern you put down on the disc.
But in order to make the information accessible to another CD drive or player , it has to be encoded in an understandable form. This format was specifically designed to minimize the effect of data errors. This is accomplished by carefully arranging the recorded data and mixing it with a lot of extra digital information. On the next page, you'll learn about the extra information encoded on a burned CD. The actual arrangement of information on music CDs is incredibly complex. And CD-ROMS -- compact discs that contain computer files rather than song tracks -- have even more extensive error-correction systems.
This is because an error in a computer file could corrupt an entire program, while a small uncorrected error on a music CD only means a bit of fuzz or a skipping noise.
If you are interested in the various ways that data is arranged on different types of CDs, check out Audio Compact Disc - Writing and Reading the Data.
With some writable CD formats, you have to prepare all of the information before you begin burning. This limitation is built into the original format of CDs as well as the physical design of the disc itself. After all, the long track forms one continuous, connected string of 1s and 0s, and it's difficult to break this up into separate sections. With newer disc formats, you can record files one " packet " at a time, adding the table of contents and other unifying structures once you've filled up the disc.
CD burners are an amazing piece of technology, and the inner workings are certainly fascinating. But to the typical computer user, the most compelling aspect of burners is what you can do with them. The cost of these storage media has fallen rapidly throughout the late s and early s, and continues to become more affordable as manufacturing costs diminish.
The burner allows this storage medium to become even more flexible than before. Initially, the acronym "DVD" was supposed to stand for digital video disc , but because it can hold any type of data, not just video, members of the inter-corporation DVD Forum refer to it as a digital versatile disc.
The DVD burner has always been more expensive, but its price has dropped as well. The DVD burner has largely displaced its predecessor, the CD burner , especially since prices have fallen to the point that most computer owners can afford them. Open your DVD burning software. Select the DVD burner you wish to use when prompted.
Select the type of files you wish to burn when prompted. Select the specific files you wish to burn when prompted. Enter in a name for your disc when prompted. Click burn. Nothing would be worse than losing your files, only to learn that you don't have a good backup either. Click to Do Nothing with it, instead of the other options it offers. Continue to select and add files from other locations on your hard drive.
If you only need the one copy, click Finish. Stay In Touch. With Information Technology Staff. Snail Mail.
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