Which type of writing on optical discs cannot be erased?

The type of writing on optical discs that cannot be erased is the write-once (R) format. In this format, data is permanently written to the disc upon initial recording. This means that once the information is burned onto the disc, it cannot be altered or deleted; it remains fixed and intact for the life of the disc. This characteristic makes write-once discs suitable for creating permanent backups or archiving data, as users can ensure that the information will not be modified or lost over time.

In contrast, rewritable discs (RW) can be used multiple times, allowing data to be erased and rewritten. Random Access Memory (RAM) is a type of temporary memory used in computers for data that is actively being processed, and it is not applicable to optical disc writing. Finally, eraseable formats typically refer to discs that allow users to delete existing data and write new data, which is not relevant to the write-once format. Therefore, understanding these differences highlights why write-once discs are designated as a fixed medium for storing data permanently.