While it is well known that DVD+R and CD+R discs are made to be recorded on only once, you may wonder why that is as opposed to the rewritable nature of “RW” discs. What stops “R” discs from being reformatted? Today’s SuperUser Q&A post has the answer to a curious reader’s question.
众所周知，DVD + R和CD + R光盘只能刻录一次，但是您可能会奇怪，为什么这与“ RW”光盘的可擦写性质相反。 是什么阻止“ R”光盘重新格式化？ 今天的“超级用户问答”帖子回答了一个好奇的读者的问题。
Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.
Photo courtesy of psc631798uk’s Trans-tography (Flickr).
问题 (The Question)
SuperUser reader Ankush wants to know what prevents DVD+R discs from being reformatted:
超级用户阅读器Ankush想知道是什么导致DVD + R光盘重新格式化：
It interests me how, no matter what computer I put a DVD+R disc in or the system installed on said computer, I am unable to format it (I know that DVD+R discs are made to be written to only once). I am guessing that it is a hardware thing, but even so, what stops a computer from ignoring the rules and formatting the disc anyway?
无论我将DVD + R光盘放入哪台计算机上或在该计算机上安装的系统如何，我都无法格式化(我知道DVD + R光盘只能写入一次)。 我猜这是硬件问题，但是即使如此，是什么阻止计算机忽略规则并格式化光盘呢？
What does prevent DVD+R discs from being reformatted?
是什么防止DVD + R光盘重新格式化？
答案 (The Answer)
SuperUser contributor Jonno has the answer for us:
Put in fairly simple terms and based on my understanding of it (I could be slightly wrong about the actual manufactured materials), I believe the process goes as follows:
- Pre-recorded discs have small holes in the surface that will prevent the reading laser from being reflected, giving you a reading of a 0 or a 1.
- Recordable discs have a dye that can be burned through by a disc drive’s writing laser. The gaps in the dye now work the same way as a pre-recorded disc would, representing a 0 or a 1 based on whether it is reflected back or not. Once this dye has been burned through, it cannot be physically recorded over again (although you could burn out the entire surface, but not make anything useful).
可记录光盘上的染料可以被光盘驱动器的写入激光烧掉。 现在，染料中的间隙的工作方式与预先录制的光盘相同，根据是否被反射回来，它代表0或1。 一旦这种染料被烧尽，就无法再进行物理记录(尽管您可以烧掉整个表面，但不能使任何有用的东西)。
- Rewritable discs use a type of metal surface (instead of a dye) that can be changed by the writing laser (depending on the power of the laser used on it). This makes the metal layer reflect differently where the laser has been, and can be “reset” by a differently powered laser.
As such, a writable disc is permanently “set” by a writing laser with no way to reset the damage it does to the dye (in order to write the data).
Further Reading: All about CD-R and CD-RW (Albeit Related to CD-R/RW Technology)
进一步阅读： 有关CD-R和CD-RW的所有信息 (尽管与CD-R / RW技术有关)
Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.
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