Optical Drives
In other words, CD or DVD. A CD (Compact Disc) is used for audio or data storage, and can hold up to 700 MB of data. A DVD (Digital Versatile Disc) is used for video or data storage, and a standard DVD contains 4.7 GB of data.
When you buy blank CDs or DVDs for recording, they may be labeled "for audio," "for video," or "for data." However, all blank optical media can be used for any purpose. The special discs for "audio" or "video" are just priced higher, but they're axactly the same as for data. For blank CDs, just get the cheapest ones. For blank DVDs, try to only buy the name-brand ones (the companies you recognize, like Sony, TDK, etc.), as the "off-brand" DVDs often fail.
There are some special terms used for optical discs:
| ROM | Read-Only (cannot record) |
| R | Recordable (but cannot erase) |
| RW | Re-Writable (can record, erase, and re-write) |
For a very long time, most computers have had a CD-ROM drive, which can only read CDs. Just about all computers today have a CD drive which can read and write CDs--this is called a CD-R/RW (CD-Recordable/ReWritable).
Most computers also have a DVD-ROM, usually in the same drive as the CD-R/RW. DVD-ROM can read DVDs, but cannot write to them. The optical drive which has both CD-R/RW and DVD-ROM is often called a "combo drive."
If you want to be able to write on blank DVDs, you will want a DVD-R/RW drive. Writing on DVDs is useful mostly in creating videos or in storing large amounts of data. Usually you can buy a CD/DVD-R/RW drive, often called a "super-drive."
| CD-ROM |
CD-R/RW |
Combo |
Super |
|
| CD-ROM |
O |
O |
O |
O |
| CD-R/RW |
X |
O |
O |
O |
| DVD-ROM |
X |
X |
O |
O |
| DVD-R/RW |
X |
X |
X |
O |
Blank CDs, bought in large numbers, cost perhaps 30 yen per CD. DVDs cost about 80-120 yen or more per blank DVD. DVDs can save about 6 times more data than a CD.
DVDs have three types: DVD-R/W, DVD-RAM, and DVD+R/W. The first two are in the same family. The last is a different family. DVD-R discs will not play on a DVD+R player, and vice-versa. However, there is a hybrid type: DVD-R, which can record and play both types. That is usually the best to get.
Regular CDs have a capacity of 650 or 700 MB. DVDs have a capacity of 4.7 GB, but special types can hold more data (dual-layer, for example, can hold 8.5 GB).
| DVD |
Single-Layer |
Dual-Layer |
| Single-Sided |
4.7 GB |
8.5 GB |
| Double-Sided |
9.4 GB |
17 GB |
HD (High-Definition) DVD
Right now, High-Definition DVDs are coming out. The two types are Blu-Ray and HD-DVD. These discs can hold anywhere from 15 GB to 200 GB.
| 1-Layer |
2-Layer |
4-Layer |
8-layer |
|
| Blu-Ray |
25 GB |
50 GB |
100 GB |
200 GB |
| HD-DVD |
15 GB |
30 GB |
-- |
-- |
The two types are not similar, and they cannot be played in the same machine. No one knows which one will become the standard type. Because they are new, they are very expensive. So buying one now can be risky: if you buy the wrong type, you will have to change to the other type later, and you will lose money. At the moment, it seems that the Blu-Ray format is winning.
