How many times can the CD-RW disc be rewritten?

About 1000 times.

Why is it possible only to write at 2x (for a 2x CD-RW disc) when the writer can support 4x rewriting?

The CD-RW disc was initially developed and sold for 2x rewriting. If one tries to write at 4x onto the 2x media, the data will be unreliable since the media cannot support writing at this speed. Therefore, to avoid 4x writing on a 2x disc there is information written on the disc about the proper rewriting speed.
In addition, RW media from RICOH, that do not have markings indicating acceptable writing speeds (1x2x4x) on the printed side, will only support 2x writing.

Why does the CD-RW disc capacity decrease to about 530 MB from 650 MB after the disc is formatted with Direct CD 2.5?

For packet writing, it is necessary that the disc be formatted. The formatting process involves writing the index information of each packet* of the whole disc. In addition, the formatting requires additional space for linking blocks as a connection between the index information of each packet.
Formatting for packet writing will require some disc space, though the size depends on the software and the version.
  • * Packet : a minimum recording unit

What does "Orange Book" mean?

The Orange Book contains the standards defined for the recordable/rewritable CD media. It is made up of three parts. In Part I; the standard applied to MO for CD is described, though this is not used at present. The main standards are Part II for CD-R and Part III for CD-RW. Each Part of these standards provides information about the signal characteristics for both a blank disc (an unrecorded disc) and a recorded disc, the mechanical characteristics, and the optical characteristics of a disc.

Page Top