what's TECHNICAL difference betwen writable CD & rewritable CD?

Question

why even after having same surface one object (Rewritable CD)can be used again an again unlike other one (writable CD)?

Answer 1

Write-once CDs are the norm. They are just that -- you can write to them once, and that's it.

Rewritable CDs require more expensive hardware and need to be erasable. You can erase and write them over. They're very rare for home users. I've used them professionally, but the equipment in question was very expensive. I don't know if there are less expensive choices.

Given the low cost of blank CDs and the high durability of the data once stored, Write-once CDs are a good choice for the vast majority of people.

Answer 2

A CD-R is a blank "compact disc - recordable". However, the music or software CD-ROM is a "compact disc - read only memory". The CD-ROMs you buy in stores are not recordable. They were never recorded. Instead they were mechanically stamped or pressed, like the old-fashioned vinyl LP albums.

Store-bought pre-recorded CD-ROMs use tiny pits or holes arranged in the tracks of the disc to encode the music, video or game software that you play. In a similar way, your CD-R burner uses laser-light bursts during your recording sessions to create tiny bubbles in the tracks around the CD-R. The burner's laser blinks rapidly on and off, heating tiny areas of the bottom of the disc which expand into bubbles that closely resemble the stamped pits of a CD-ROM. Later, when the CD-R is played back, the CD-R is now actually a CD-ROM. CD players read CD-R and CD-ROM discs equally well in almost all cases. (A few CD players may have difficulty reading CD-R discs, but playback problems are usually caused by scratches, poorly applied or too-heavy off-center CD labels, and discs that have been exposed to heat or UV light -- discussed below.)

You have probably heard of several types of CD-ROM discs, including those that contain music, software, video, photos, and games. On each of these types of CD-ROMs, the data is formatted differently. CD players are made to be able to read or decode each of these CD-ROM formats so you can easily use the disc, without knowing much about its contents. CD-R discs can be burned in the same formats as CD-ROMs, and played the same simple, easy way. CD creation software lets you select the final format of the disc you're creating. After you make a few optional decisions, the actual recording of a CD-R is usually quite simple. See the manual for your CD creation software for more details.

Once fully recorded or burned, a CD-R disc cannot be erased and used over. Therefore CD-Rs are sometimes called "write-once" discs. There are also erasable "re-writable CD-RW" discs. CD-RW discs are sometimes called "write-many-times" discs, and can be fully erased and re-written up to 1,000 times. Unlike CD-Rs, CD-RWs cannot be played by most CD players. They are for data storage and editing uses in computers. We discuss CD-RWs in detail under question #12 below.

Answer 3

While a prerecorded compact disc has its information permanently stamped into its polycarbonate plastic substrate, a CD-RW disc contains a phase-change alloy recording layer composed of a phase change material, most often AgInSbTe, an alloy of silver, indium, antimony and tellurium. An infra-red laser beam is employed to selectively heat and melt the crystallized recording layer into an amorphous state or to anneal it at a lower temperature back to its crystalline state. The different reflectance of the resulting areas make them appear like the pits and lands of a prerecorded CD.

A CD-RW recorder can rewrite 700 MB of data to a CD-RW disc roughly 1000 times. CD-RW recorders can also write CD-R discs. Except for the ability to completely erase a disc, CD-RWs act very much like CD-Rs and are subject to the same restrictions; i.e., they can be extended, but not selectively overwritten, and writing sessions must be closed before they can be read in CD-ROM drive or players. The UDF 1.5 file system allows CD-RWs to be randomly rewritten, but limits disc storage capacity to roughly 530MB.

Written CD-RW discs do not meet Red Book or Orange Book Part II standards for prerecorded or recordable CDs (e.g. reduced signal levels). Consequently, CD-RWs cannot be read in CD-ROM drives built prior to 1997. CD-R is considered a better technology for archival purposes as disc contents cannot be modified and manufacturers claim greater longevity.

CD-RW discs need to be blanked before reuse. Different blanking methods can be used, including "full" blanking in which the entire surface of the disc is cleared, and "fast" blanking in which only meta-data areas are cleared: PMA, TOC and pregap, comprising a few percent of the disc. Fast blanking will obviously be much quicker, and is usually sufficient to allow rewriting the disc. Full blanking removes traces of the former data, often for confidentiality. Data from "fast" blanked CD-RW discs can be recovered by some software like the Linux version of PhotoRec.

Answer 4

A writable CD can only be written to one time. A rewritable cd can be written to, erased and rewritten to several times.

Answer 5

the technical difference is the heat used to burn the cds...a cd-r uses a higher heat and thus produces better quality (it is able to played in almost all cd players)...whereas, a cd-rw uses less heat for the burning process and the quality is different (i don't wanna say poorer) than the cd-r and thus it not able to be played in all cd players unless it specifically states that it can play cd-rws....