虽然众所周知，DVD+R和CD+R光盘只能刻录一次，但您可能想知道为什么这与“RW”光盘的可重写特性相反。是什么阻止了“R”光盘的重新格式化？今天的超级用户问答帖子回答了一位好奇的读者的问题。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

图片由psc631798uk的Trans-tography（Flickr）提供。

问题

超级用户阅读器Ankush想知道是什么阻止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?

什么可以阻止DVD+R光盘重新格式化？

答案

超级用户贡献者Jonno为我们提供了答案：

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 **all 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).
• 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)

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