The next option to consider when choosing recordable CD-R/RWs is the capacity of the media you use. CD-Rs and CD-RWs are easily available in 650MB/74min and 700MB/80min sizes, though larger capacities can be found.

Consistent with the speed rule listed above, the newer the drive, the less likely it is to have difficulties with higher capacity media. Older drives may have issues because of the increased density of the data tracks in the higher capacity disks. Any writer made within the last 3-4 years should be fine with at least the 650 and 700MB media.

The last possible issue is the colour of the CD-R. Now this was a really hot topic a few years ago when CD writers were coming onto the mass-market, with heavy debates on all sides. The issue is which combination of dye and reflective material provides the best compatibility, and which dye gives CD-R media the most longevity?

The colour of the bottom of a CD-R disk is a combination of the dye type and the reflective layer of metal. For example, the combination of Cyanine (one of the most popular dyes) and a silver reflective layer results in a blue/green sheen. Older writers were noted for liking some colour combinations better than others, resulting in a lot of wasted CDs and frustration.

Again, any newer CD-RW drive should not be particularly fussy when it comes to the colour of the disks you feed it, but the best method here is to visit the manufacturer's website and check their list of compatible media. Come to think of it, this is the best method for dealing with all the issues we've just listed.

The subject of data-fastness and longevity of CD-media is still being debated, and likely will be for a while. Artificial 'rapid-aging' tests on various CD-R media types have shown that gold reflective disks seem to hold readable data for longer than other colours of CD. Some estimates give as long as a hundred years before the dye becomes unreadable, even the cheapest of disks is likely to hold its data for more than a decade, provided it is well cared for.

DVD formats, the battle continues: To understand the variety of options available in the area of DVD authoring, it's necessary to understand how the physical media, the DVDs themselves, work.

DVD-ROM or "Digital Versatile Disk - Read Only Memory" media is currently available in four forms. DVD-5, DVD-9, DVD-10 and DVD-18. It can be single sided (DVD-5 and -9) or double sided (DVD-10 and -18), and each side contains a single data layer (DVD-5 and -10) or two data layers (DVD-9 and -18). DVD-ROMs are the equivalent of 'stamped' CDs and are mass-produced via injection molding techniques as detailed above. They are not writeable.

DVD-R is the original format for writeable DVD disks, as put forward by the DVD Forum, an assembly of interested companies founded by Pioneer, Panasonic, Sony and Time-Warner among others. DVD-R disks use much the same method as CD-R disks to store information. A dye is inserted between the layers of polycarbonate which can be selectively darkened by the 'write' laser of the DVD-R drive, so as not to reflect the 'read' laser.

Unlike DVD-ROMs, DVD-R disks can have only a single data layer on each side of the disk, making for capacities of 4.7GB single sided and 9.4GB double sided. DVD-R disks can be played back on most commercial DVD players and drives. They can be written using one of two methods; the 'disk at once' method burns all required data onto the disk in one continuous write process, then finalizes the disk so that no more writing is possible. This disk will then be readable in most DVD players and drives.

Incremental writing can also be done, in which individual files are added to the disk until it is full, or the author decides to finalize (or close) the disk. While this is more flexible, it has the disadvantage that only other drives capable of writing DVD-R disks will be able to read the media before it has been finalized. The Apple 'Superdrive' is a DVD-R drive. Since the recording process is similar, most, if not all DVD-R drives can also write to CD-R media and usually CD-RW also.