CD-ROM. (in English C ompact D isc- R ead O nly M emory, “Compact Disk-Read Only Memory” according to ABBREVIATIONFINDER). It is a flat plastic compact disc where digital information is recorded on its surface in small aligned “grooves”. Recorded information is encoded in a spiral from the center to the outer edge. Medium used to store non-volatile information, which is read optically.

Capacity

On a standard CD-ROM you can write from 650 or 700 and sometimes 800 MB of data. This data carrier and storage medium is popular for the distribution of software, especially multimedia applications, and large databases; and weighs less than 30 grams.

Storage and Cleaning

In order for the disk to store all data in its entirety and for a very long time, it is necessary to keep the disk in the correct packaging or places. The reflective part (or parts) of the disc must be clean and scratch-free to avoid data loss. It is a good idea to transfer data from an old or eroded disk to a clean or new disk before all data is lost over time.

Cleaning the disc is only recommended if it is very dirty and there are image and / or sound skipping, or reading errors. Since error correction systems can read the data through a moderate amount of scratches and / or fingerprints.

If the disc is only dirty, it is recommended to wipe it with a soft cloth (or cotton) in one-way movements, from the center of the disc outward. A disc should never be cleaned in a circular motion to prevent dirt or dust from damaging the data on the disc. If the disc is too dirty, it is advisable to immerse it in water and then clean it, after which it must be allowed to dry very well before reading or recording on it (it is inadvisable to use a hair dryer for this, since hot air produces steam that could warp the disc). If the disc is scratched and dirty, it is recommended to clean it in the manner that applies the condition, and try to read the disc. If no data errors occur, or most of the data is intact,

The best packaging for the disc is the one the disc comes in when purchased. You can also use disc holders or disc albums (as long as they are of good quality).

The disc must never be written or painted on its reading side (the non-screen printed one), to avoid reading or writing errors. Discs can be identified in the specialized part (in the instructions or on the disc) with a special marker and never with a pencil or ballpoint pen, to avoid causing cracks on the disc.

No papers or stickers should be attached to the disc, except in the case of labeling systems specifically designed for this medium. An adhesive that is not symmetrical with respect to the center of the disc could shift its center of mass and produce unwanted vibrations during reading.

In some cases, a badly damaged or cracked disk is likely to break inside the disk’s read or write drive. In this case, it is advisable to turn off the device or equipment and contact a specialized person, in order to avoid further damage. If no specialized person is available, the read or write unit can be removed from the equipment, until another is available.

Multisession

Computer programs have long emerged to burn CDs that allow us to use a CD-R disc as if it were a rewritable disc. This does not mean that the CD can be recorded and later erased, but rather that it can be recorded in different sessions, until it occupies all the available space on the CD.

Multisession discs are nothing more than a normal recordable disc, neither in their boxes nor in the information about their technical details it is highlighted that it works as a Multisession disc, since this function does not depend on the disc, but on how it is recorded.

If a CD is recorded and it is not finalized, we can add a new session to it, wasting a part to separate the sessions (about 20 MB approximately).

We will make a CD multisession at the time we make the second recording on it, whether it is finalized or not. However, when recording a music CD, the CD-R is automatically finalized and cannot be used as a Multisession disc.

Not all devices or operating systems are capable of recognizing a disc with multisession, or that is not finalized.

Differences between multisession CD-R and CD-RW

There may be confusion between a CD-R with multisession recording and a CD-RW. At the moment when a CD-R disc is made multisession, the software will give it the characteristic that it can be used in multiple sessions, that is, “sessions” will be created for each recording, which will only be modified by the user. see fit. For example, if the files test1.txt, test2.txt, and test 3.txt have been burned to a CD-R, a session will have been created on the disc that will be read by all players and will contain the above files. If at any time any of the files are not needed or the content of the recording is modified, the software program will create a new session, after the previous one, where the files that you do not want to consult will not appear, or the modifications will be seen performed, that is, it is possible to add more files, or even remove some that were included. When making a modification the previous session will not be erased, but will be hidden by the new session giving a feeling that the files have been deleted or modified, but in reality they remain on the disk.

Obviously the previous sessions, although apparently they do not appear, they remain on the disk and are occupying space on it, this means that one day it will no longer be possible to “re-record” it, modify the files it contains, because the full capacity of the disk will have been used..

Unlike CD-Rs, CD-RW discs can be erased, or even formatted (it allows you to use the disc, losing a part of its capacity, but allowing you to record on new files). In the case of using a CD-RW when we erase, we erase it completely, partial erasures can also be made, which need a higher laser power to be recorded again. A CD-RW disk can be used like a floppy disk, with suitable software, as long as the unit supports this feature, files can be manipulated as on a floppy disk, with the exception that it is not erased, but when erasing a file it continues occupying a space on the disk, although when examining it, this file does not appear. CD-RW discs require more laser power to be able to record,

DVD-RW, DVD + RW work in an analogous way, DVD- RAM also, but they are designed for writing as with floppy disks.