Learn in the textbookOptical Disc Storage Media — CD, DVD, Blu-ray
DefinitionA DVD-RAM is a DVD whose recorded data can be rewritten any number of times, so files can be added, deleted and overwritten again and again.
ExplanationIts recording layer uses a material that switches between a crystalline and a non-crystalline state depending on how it cools after laser heating, and the difference in reflection between the states encodes the data (phase-change recording). Because the state can be switched over and over, the same spot can be rewritten repeatedly. DVD-RW is also rewritable, but DVD-RAM is built to make small-unit reads and writes easier, much like a hard disk.
AnalogyLike a whiteboard, where you can write and wipe the same surface over and over.
Memory hookRAM stands for Random Access Memory, a name that means any location can be read or written. It shares the name with the RAM of main memory, but it works differently.