R/W

Updated: 12/10/2023 by Computer Hope

R/W may refer to any of the following:

1. Short for Read/Write, R/W is a file attribute or permission given to files and directories that allow them to be read or written. These attributes can also be removed to prevent that file from being read or modified.

Computer CD-RW drive and disc

2. Short for re-writable, CD-RW (compact disc re-writable) is a drive and CD (compact disc) media created in 1997 that could be written to and read. Unlike a traditional CD-R (compact disc recordable) disc that can only be written to once, these discs allow data to be erased and re-written multiple times.

Note

CD-RW was featured as a top term of 1998.

How does a CD-RW work?

The CD-R technology uses a photosensitive dye. CD-RW discs use an active layer of Ag-In-Sb-Te (silver-indium-antimony-tellurium) alloy that, in its original state, has a polycrystalline structure that makes it reflective. When the CD-RW drive writes to the disc, the laser uses its highest power setting, called Pwrite. At this temperature, which is usually between 500 and 700 degrees Celsius, the chemical structure will liquefy. In its liquid state, the molecules of the active material flow freely, losing their polycrystalline structure and taking on an amorphous state. When the material solidifies in this amorphous state, it loses its reflectivity. By selectively firing the laser, the drive leaves parts of the disc in its polycrystalline state, forming the lands, and parts in the amorphous state, forming the pits.

To reverse the phase of a specific area on a disc, the laser operates at a lower power setting and heats the active material to approximately 200 degrees Celsius. By heating the disc, it reverts from its amorphous to its polycrystalline state and then becomes reflective again.

The drawback with CD-RW discs is that the lower reflectivity of the disc can limit the readability. In the 1980s, CD standards specified that compact disc lands should have a minimum of 70% and the pits 28% reflectance. However, on a CD-RW disc, the reflectance of a land is approximately 15% to 25%. The low reflectance can cause some CD-RW discs to be unreadable in older CD-ROM (compact disc read-only memory) drives and CD players.

3. The Internet domain suffix .rw is short for Rwanda.

CD terms, Computer acronyms, Orange book, RW head