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If you've read my article on the Floppy Drive you'll know that venerable medium originated in 1971. What you may not know is that he CD itself was released in 1983 and even the DVD as a technology is ten years old this year (2006). Between them these two data storage formats have brought multimedia to the PC and effectively made the floppy disk obsolete. Before looking at the drives themselves I'll delve a little into the history of the media themselves.

The CD:

A compact disk 'CD' is a binary optical data storage medium originally intended for digital audio. The format we know today evolved from Phillips' Laserdisc technology of the 1970s. By the late 1970s a number of companies presented prototypes for digital audio disks and in 1979 Phillips and Sony decided to join forces. From their collaboration the compact disc was invented and reached marked in Asia during 1982. Three years later, in 1985, the CD-ROM (Compact Disc Read Only Memory) was introduced. This led to the eventual adoption of the CD as the primary method for the distribution of operating systems and software.

During the early 1990s the first user-recordable CDs (CR-Rs) were introduced and this quite quickly became to standard for the storage and exchange of both computer data and music. The birth of the CD-ROM (and subsequent computer-compatible CD formats) were based a standard published by Sony and Phillips in 1985 (this is called the Yellow Book standard) which defined a data-storage standard readable by a computer with a CD-ROM drive.

The CD-ROM Drive

The CD-ROM drive is now almost universal on all personal computers (though they are slowly being replaced by DVD drives and 'combi' drives [see below]) and are generally connected to the motherboard by an IDE (ATA) cable (though some systems may use SCSI connections). All CD drives use a laser to scan the surface of a CD and read the hills and troughs in the disc's surface (converting these to binary 1s and 0s, respectively). Each drive is also given a speed factor which is measured relative to a music CD. With a 1× disc having a transfer rate of 150kb per second. Initial versions of CD drives had a special caddy to hold the disc itself but this was never truly popular. Rather, the tray-loading mechanism became the standard with the CD being dropped into an indentation in the tray. Current CD drives are reaching a speed of 52× which is near the physical limit at which the disc itself can be spun; with the speeds generally represented in that order. With the appropriate software such drives can also play audio CDs and Video CDs (VCDs).

What truly made the CD drive an indispensable item of computer equipment was the ability to write CDs (colloquially termed 'burning') as well as being able to read them. Most modern CD writers can record both recordable CDs and re-writable CDs (CD-RW) and typically have three speed ratings: one speed for write-once operations, one for re-write operations, and one for read-only operations.

The DVD:

The Digital Versatile Disc (DVD) represents the latest generation of optical storage media. In size it closely resembles a CD, however its data storage capacity is much higher and the obverse of the respective discs have different light-scattering properties. The modern DVD arose out of work during the early 1990s to generate a high-density optical storage standard. Two competing standards (MultiMedia Compact Disk MMCD) and (Super Density Disc SD) emerged though both camps were eventually persuaded to emerge with a common standard. This was published in 1995 and finalized in 1996 specifying a disc with a storage capacity of 4.7Gb (almost six times the amount that would fit on the best CD of the time). As with CDs the first DVDs to reach market were read-only movie discs. It took a few years for DVD players to reach a price where they were reasonable to purchase and video tapes remained the dominant force in movie sales. However the years between 1999 and 2006 saw the rise and rise of DVDs to be the medium of choice for buying films.

In 1996 the DVD forum published a standard for data called DVD-RAM and this has been utilized for computer discs as well as for camcorders that record directly to DVDs. This technology has the advantage that it works like a hard drive and can be read directly by a computer. DVD-RAM is not the only standard for computer discs, however. One of these is DVD-R (DVD-Recordable) and the related read/write format DVD-RW. There is also the competing standard DVD+R and DVD+RW. Though they are overlapping technologies they are not completely compatible and a DVD-R drive will not write DVD+R discs. For this reason hybrid DVD±RW drives have become popular.

As computer software is becoming more complex and the use of video and audio in computer applications is increasing more and more software is being released on a single DVD rather than multiple CDs. Thus a DVD drive is fast becoming an essential piece of computer equipment.

The DVD-ROM Drive

Because of the competing DVD formats there are DVD drives that write to both the '-' and '+' standards separately as well as drives that write to both. Almost all DVD drives will also read several CD formats so that the drive is still compatible with software and data delivered on CD. There is also the advent of the 'combo drive' that can read and write CDs as well as being able to read DVDs. If you're on a budget this is the drive to get for your new machine. If, however, you can afford it then you really should buy a combo drive that can also burn DVDs as well as reading them. This gives you the best of all possible worlds.

DVD, the Future?

Like almost all computer-related technologies the purported successors to the DVD format are already approaching production. The two main contenders at the moment are Toshiba's HD DVD and Sony/Panasonic's Blu-Ray Disc. Both consortia have now produced examples of readers that are compatible with existing DVDs and though the Blu-Ray technology allows for greater data density (25Gb as opposed to HD DVD's 15Gb), HD DVD is compatible with existing manufacturing technology whilst Blu-Ray is not.

There will be a battle between these two technologies for high-definition movie sales they may be too little too late for use as computer technology. Though drives based on both Blu-Ray and HD DVD will undoubtedly become available the reality is that large removable hard drives and solid-state drives may beat them to the post.

However, as we await the latest emerging technologies and view the inevitable format wars from the sidelines the best option we have for our PCs at the moment is a DVD drive. If you're buying components for your PC now then get a DVD 'combo' drive.

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