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Difference between CD-R and CD-RW. RW disks. What it is

QUESTIONS AND ANSWERS: What you need to know about CD-R recordings and CD-RW discs.

1. What do you need to have to burn CDs?

You need a computer with a device installed in it called a CD-writer. This device connects to the computer in several possible ways. Most disc burning drives have an IDE interface and connect in the same way as regular CD-ROMs or hard disks and have internal execution. However, there are other versions, both external and internal - with a SCSI interface, connecting to a parallel port or to USB bus.
The second necessary part for burning discs is software. Its choice is very large - from the most popular commercial packages from Adaptec (Easy CD Creator, Easy CD Deluxe, Easy CD Pro) to shareware programs such as Nero or CDRWin.
And finally, you need a blank CD-R or CD-RW disc

2. What can you burn onto CD-R or CD-RW discs?

Traditionally, discs can store both sound and data. Data is stored on CDs in the same format as it is stored on a hard drive. It should also be noted that it is possible to create mixed discs, combining sound with data.

3. What's the difference? CD-R discs and CD-RW?

CD-R stands for CD-recordable, that is, “recordable.” This means that information recorded on such a disk cannot be deleted from there. The main difference between CD-RW (CD-rewritable) discs is that information from them can be deleted and recorded again. As a result, CD-RW discs, which are more flexible in use, are slightly more expensive than conventional write-once discs.

4. How much information can be recorded on a CD-R disc?

5. Why is the standard duration 74 minutes?

The general consensus is that this length was chosen because the CD developers wanted a format that would accommodate Beethoven's Ninth Symphony. They determined which diameter to use, and the length of some performances decided this issue.

Recorded discs can be used on the following devices:

DVD-ROM drives

All modern CD-ROM drives read excellently, both write-once discs and CD-RW discs. Nuances exist only with old drives, which in some cases do not read CD-R discs, or read these discs, but do not read CD-RW discs. If your old drive is marked as having a Multiread function, then this means that you can use it to cope with this task. A good indication that a drive is capable of handling recordable discs is how fast the drive reads data. If the speed is 24x or higher, then, as a rule, such a drive is quite suitable for working with CD-R and CD-RW discs.

7. Why are the reflective sides of the discs different colors?

Different CD companies have patents on the various chemistries they use to produce the discs. Some companies produce disks themselves, others simply license their technology to them. As a result, the reflective side of CDs comes out different colors. CD-Rs are available in the following composition combinations: gold/gold, green/gold, silver/blue, and silver/silver, and their many shades. The visible color is determined by the color of the reflective layer (gold or silver) and the color of the dye (blue, dark blue or clear). For example, green/gold discs consist of a gold reflective layer and a blue dye, so the disc is gold on the label side and green on the recording side. Many have come to the conclusion that "silver" discs are made of silver and, based on this assumption, have tried to speculate about the reflectivity and durability of the media. Until a manufacturer's representative comes forward with a statement about the actual composition of the disc, it is unwise to assume anything specific. Some CDs have additional coverage(such as Kodak's "Infoguard"), which makes the CD more resistant to scratches, but does not affect the way information is stored. The top (label) side of the disc is the most important area to worry about because this is where the data lives and is the area that is most easily damaged on a CD-R. You can protect the disc from scratches by sticking a round CD sticker over its entire area. CD-RW discs have a completely different structure. The data side (as opposed to the label side) is a silvery dark gray color that is hard to describe. You can also give a short list of which companies produce which discs:

Taiyo Yuden produced the first "green" CDs. They are now also made by TDK, Ricoh, Kodak, and probably a few other companies.

Mitsui Toatsu Chemicals (MTC) produced the first "golden" CDs. They are now also made by Kodak and possibly others.

Verbatim produced the first "silver/blue" CDs.

Many brands of CD-R (such as Yamaha and Sony) are OEM versions of one of the major manufacturers. By and large, it is difficult to determine who produces what, since new plants have been built and sellers may change suppliers.

8. What do the speed numbers (for example, 6x4x32) mean in the parameters of CD burners?

Conventional audio players play music CDs in 74 minutes. This speed taken as the basis for measuring the speeds of playing and recording CDs and called single speed (1-x). Single speed corresponds to a transfer of 150 Kilobytes per second. A CD-ROM drive with two times the speed (2x) transfers data at a speed of 300 Kilobytes per second.

Three numbers in the parameters of CD-writers indicate the speed at which this device can write CD-R discs, CD-RW discs and read these discs accordingly.
For example, 6x4x32 means that this device writes CD-R discs at a speed of 6x (900 KB/sec), writes CD-RW discs at a speed of 4x (600KB/sec) and reads any type of CD at a speed of 32 (4800 KB/sec)

9. What formats exist when burning CD-R discs?

This is the most difficult question to answer, given that many different CD formats have emerged over the past few years, while there are still historical formats that have been around for a long time and are used in specialized applications. Below is an overview of the main formats:

Music discs (Audi o CD) or CD-DA or "Red Book"

To burn regular music CDs, you need the disc you burn to conform to the CD-DA standard. When recording, standard WAV files (or AIFF - Apple Audio Interchange File Format) are used as a source.

ISO9660 Data CD

This standard defines the form in which conventional data is written to CD-R discs. This standard has many restrictions, namely, the maximum number of subdirectories cannot exceed 8, file names cannot be longer than 8 characters, and 3 characters are allocated for the file name extension. However, this standard is compatible with a large number of computers and operating systems.

The format proposed by Microsoft simultaneously with the advent of the operating system Windows systems"95. The file name length is limited to 64 characters in this standard, and this format is now supported, as in Windows environment, and on MacOS and Linux. Joliet is based on the ISO9660 standard and discs written in this format can be read on almost any computer. However, filenames will be truncated to 8+3.

This format strictly applies to Macintosh computers. HFS CDs can only be read on this type of computer.

UDForPocket Writing

UDF (Universal Disk Format) is a radical extension of the ISO9660 standard, somewhat reminiscent of Joliet. Adaptec DirectCD software (included with Easy CD Creator Deluxe, or sold separately for the Mac platform) and, for example, CeQuadrat PacketCD software allow you to burn discs in this format. UDF differs from other formats in that you can treat a CD like a large floppy disk, copying files to it using standard Windows tools or MacOS. However, this format is not suitable for transferring discs to other people, because in order to read discs in this format, they will need to install special software for reading such discs.

ISO 9660 Rock Ridge

Extension of the ISO9660 standard, used exclusively in operating rooms Linux environments and UNIX.

ISO Level 2

A slightly modernized ISO9660 format, simplified in terms of restrictions. For example, the file name length in it is limited to 31 characters. However, the low level of compatibility of this standard does not allow it to be used as widely as, for example, the Joliet format is used.

VideoCD or VCD or "White Book"

The VideoCD format was developed in the mid-90s and was intended for use in devices such as the Philips CD-I player. VideoCD discs contain video image and audio compressed using the MPEG1 standard. Despite the fact that the Philips CD-I player has not been produced for a long time, these discs can be used on the vast majority of DVD players if they support reading CD-R or CD-RW discs.

8. What format should I use if I want….

…. exchange data with friends who use an operating system similar to mine?

Everything is simple here. Windows operating system users should use the Joliet format, Mac users should use the HFS format.

…. share data with people who use different operating environments and platforms?

For maximum compatibility, it is recommended to use the ISO9660 format. However, if you need to save long names files on disk, then you should try using the Juliet format. Modern Macs and most operating systems now have the ability to read discs written in this format.

…. listen to music on a regular audio player?

Then you should burn the disc in CD-DA format, which will provide the highest level of compatibility with your audio player.

10. How to burn discs with mixed content?

There are two options for burning such discs:

Mode I- using of this format the data is recorded at the beginning of the disc (in any known format), followed by the recorded audio tracks. If you need to combine audio and data, then using this mode will provide the necessary level of compatibility with various devices and operating environments.
CD-XA (Mode II)- this mode differs from the previous one in that data and sound can be recorded in random order. However, this flexibility has a negative impact on the compatibility of the recorded discs.

11. What is a multisession CD?

This technology allows you to add data or sound to a disc that already has something written on it until the disc is closed. This was very relevant in the early 90s, when the cost of a blank CD-R disc reached $12, CD-RW discs did not exist, and hard drives had a small capacity.

Discs recorded using this technology have some compatibility issues, and therefore it is not recommended to use it without compelling reasons. The UDF format makes this technology unnecessary; using Direct CD and similar software you can record data without worrying about compatibility. If you need to give the disc to other people, then just burn it at once in Joliet format

12. What is "closing" a disk?

"Closing" a disc means that after this procedure is completed, nothing can be done on that CD-R disc. If you never use the "multisession" feature, then there is no point in thinking about it, because the disk will close automatically after the end of writing information to the disk. Many older CD-ROM drives and audio players have problems reading unsealed discs, so it makes sense to "seal" the disc for greater compatibility.

If you want to write something to a "closed" CD-RW disc, simply perform the "clear" function and you will be able to write data to that disc again. If you use the UDF format, then there is no concept of “closing” the disk in the traditional sense of the word - just copy and delete files from such a disk, as from a simple floppy disk.

If you insert a blank CD-RW or DVD-RW disc into the drive, Windows 7 Explorer will automatically prompt you to format this disc when you try to open this disc:

LFS this is nothing more than a UDF. File system for batch burning to CD and DVD discs. Allows you to use a laser disc in the same way as a regular one. That is, copy and delete files in the simplest way. The UDF file system is particularly used in DVD-Video.

Mastered this is a disc burn to file system ISO9660 with Joliet extension. The ISO9660 file system is the traditional file system for laser discs. Audio CDs, MP3 discs, discs with computer programs are written to this file system.

Using the UDF File System (LFS)

The UDF file system is used for batch recording on laser discs. Depending on the version, it is supported by different Windows versions. For example, Windows XP supports versions 1.50, 2.0, 2.01.

The UDF file system is also used in video and audio recording and playback systems, for example in DVD players (DVD-video discs are made using UDF version 1.50). There are video camera models that record filmed material onto DVD-RW discs. In order to use such disks, you first need to format it.

Insert a blank CD-RW or DVD-RW disc into the drive, then Windows 7 Explorer will automatically prompt you to format this disc when you try to open this disc:

Formatting in the file system can take quite some time, for example, a CD-RW 700 mb can be formatted in 10 - 12 minutes.

After formatting is complete, you can copy files to this drive directly through Windows Explorer:

However, you need to remember that the copying speed to a UDF disk is much lower than to a regular or USB flash drive.

The era of CDs is slowly but surely becoming a thing of the past. Now most modern users don’t even know how they differ from standard R and ROM. In order to understand the difference, you need to remember the history of their creation. Only then will it be possible to determine their main difference from classic CDs.

History of the development of optical CD media

The first compact disc was developed by Philips. They are considered pioneers in this field. At first, optical disks had rather little space to store data. The initial volume of such a “blank” was 640 megabytes. But over time it increased to 700. The first optical discs in the compact format were called CD-R. This meant that data could only be written to them once. For a long time they were used as carriers. However, time passed, technology developed, and very soon manufacturers introduced the CD-RW rewritable compact disc. This abbreviation (RW) comes from the English word Rewritable (with the ability to rewrite). Such optical media have become incredibly popular among users. The very idea of reusable recording to disk seemed incredible. But there was one minus. The recording speed on such media was very low. If the standard R disc was written at x53 speed, then RW Classic discs needed to be written at x6 speed. But this did not last long, as standard CDs soon went out of fashion.

The advent of DVD

The decline of classic "compacts" is directly related to the emergence of a new format - DVD-R. These optical drives were distinguished by their gigantic volume (compared to CDs). They could fit 4.5 gigabytes of information. It was a breakthrough. As expected, some time after the successful launch of classic DVDs, DVD-RW discs appeared that allow you to record on one or another medium several times. And this solution has become incredibly popular.

DVD discs were used almost everywhere: programs were recorded on them, OS, films and other information. Even music in formats without loss of quality was written on DVD discs. And in this regard, DVD-RW discs looked like the most universal solution. And soon double-layer DVDs appeared that could hold almost 10 gigabytes of information. This was truly a breakthrough. For a long time, DVDs were used everywhere. Special players were also released. They could read RW as well, so users recorded several movies on them at once. And when they got tired of them, they re-recorded them. This went on for quite some time. But the DVD era has come to an end.

Blu-Ray era

Classic and double-layer DVDs have been replaced by Blu-Ray media. They were distinguished by increased capacity. One such disk held about 25 gigabytes of information. That's a lot. Around the same time, HD video formats also appeared. Films in this format fit perfectly on BD. This determined the area of application of such optical media - the film industry.

Indeed, keeping the library on BD was somehow wrong. Moreover, at the same time, the Internet developed rapidly and large-capacity USB drives appeared. Nobody needed disks anymore; only BDs were still afloat. And that’s only thanks to those who like to watch movies in maximum quality in their home theater. Over time (as expected), dual-layer BD and BD-RW discs appeared. The latter allowed information to be overwritten. But considering the volume of Blu-Ray media and low speed recordings on RW, this option has not gained popularity. To this day, BD-RW remains just an interesting technology. But nothing more.

The relevance of Blu-Ray technology is also being rethought. New video resolutions have appeared - 2K and 4K. But they require much more space and will never fit on a classic BD “blank”. The era of Blu-Ray will probably soon end successfully. But that's a completely different story.

Conclusion

So, we talked about the features of RW disks and looked at the history of the development of optical media. Classic CDs are already used exclusively in music industry. No one has heard of DVD for a long time. Nowadays Blu-Ray technology rules the roost. But judging by the latest trends in the world of multimedia entertainment, the days of the technology described above are numbered. Perhaps manufacturers are now developing a new type of optical media. But we’ll tell you about what happens next next time...

Before CDs become museum rarities, it would be nice to remember how CD-R differs from CD-RW. It is these optical media that are familiar to us as “blanks” on which any information that fits into the volume can be recorded.

CD-R(Compact Disc-Recordable) – a compact disc that allows information to be written to it once.

CD-RW(Compact Disk ReWritable) – a rewritable CD.

The external difference between a CD-R and a CD-RW is manifested in only one thing: its type is indicated on the box and surface of the disc. The physical dimensions are standard; any modern optical drive works with both. Today they are used in most cases as bootable CDs (for older operating systems), a means of exchanging data between systems when no other option is possible, and also in players. Sometimes duplicated on CD-R important information: It is impossible to erase it from this media either accidentally or intentionally.

Comparison

So, on a CD-R we save data and subsequently only have the ability to read it, but a CD-RW can be completely erased and written again an almost unlimited number of times. You can endlessly twirl these discs in your hands, but still not see the differences.

How does a CD work? A thin layer of metal is applied to the plastic base, on which spiral tracks with indentations are created during recording; everything is covered with a transparent varnish to protect it from physical damage. During sensing, the laser beam is reflected differently from deformed and non-deformed areas, and such signals are interpreted by the receiving device.

This applies to read-only disks. The user must also write down the blanks, so another layer is added to their design on top of a reflective substrate made of gold or silver film. Its properties determine the difference between CD-R and CD-RW.

For CD-Rs it is organic. During the recording process (called burning in home systems), the laser heats certain points until they darken, and when reading, the light from the substrate is reflected more intensely where the layer storing the information remains transparent.

For CD-RW, everything is somewhat more complicated: the recording layer is made of a special metal alloy, which, when strongly heated by a laser, goes from a crystalline state to an amorphous one (in other words, it turns glassy). The refractive power of the material is different in different states, so the amorphous regions play the role of pits. When erased, medium-intensity heating returns the layer to its original crystalline state. Similarly, information on one disk can be rewritten many times.

Phase transitions after a certain number of write-erase cycles destroy the material of the recording layer, so CD-RWs are considered less durable and reliable media than CD-Rs. However, in practice, optical disks fail only as a result of mechanical damage.

For CD-RW, a minimum recording speed is established, below which the transition of a substance from one state to another is simply impossible. Maximum speed values are regulated for both types: if exceeded, the burning will be of poor quality, the points will be “smeared”.

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