Know the difference between your RAMs and your ROMs? What about the RW? Jane Wakefield explains it so your mum will understand... DVD -- or Digital Versatile Disk -- is the storage media of the future, set to leave CD-ROM dead in the water by the year 2001 according to figures from industry analyst Dataquest. But DVD is essentially the same technology as its older sibling the CD-ROM. The pits and groves in a disk are read by a laser which converts the pits into digital data. In order to squeeze in more data than on traditional CDs the pits on a DVD disc are smaller and the tracks are closer together. The most significant difference is that DVDs can be two-sided and double layered giving the format up to 25 times more storage space than a CD. With movies the most attractive and obvious application for DVD the movie studios had to be kept happy. The studios challenged the DVD Forum -- responsible for DVD standards -- to create a system that protects their investment in new films. The somewhat bizarre Content Scrambling System (CSS) -- also known as 'regional coding' -- was born. The CSS is a series of regional settings that exist on the same format but are incompatible with each other. So a player in region 1 will not play discs bought in region 2 and vice versa. Region 1 includes the US and usually gets the latest film releases first, so if you bought your (region 2) DVD player in Europe, American disks won't work. DVD players also come in two types: the set-top box linked to the TV like a VCR, or more popular at present, a drive for PCs. And while the battle between DVD drives looks set to escalate over the next year or so it could be overshadowed by the battle between rival DVD formats. Whereas CD ROM had a long period of grace before the CD rewriters arrived, DVD RAM is already competing with DVD ROM as the next generation format. The difference is simple: DVD ROM can only read data whereas DVD RAM can read, write, rewrite and erase. Creative's European brand manager Franco de Bonis thinks the battle between ROM and RAM will be won on price. "Whereas a DVD ROM drive is available for under £100, an equivalent RAM drive will cost about £500," he says. DVD RAM is more difficult technology to implement according to de Bonis. "Rewriteable technology is incredibly complicated," he says. Driven by the technology behind CD rewriters -- which only needed tweaking to produce DVD RAM -- the format would have mass appeal, allowing a DVD player to perform the same tasks as a VCR. Editor of One to One and chairman of the upcoming European DVD conference Tim Frost thinks DVD RAM is what the consumer is waiting for. "The man in the street doesn't care about formats. All he cares about is being able to play whatever DVD discs he has on one machine." An at a glance guide to the formats: DVD ROM The read only format. One million drives shipped in Europe in 1998. IDC analyst Bob Peyton predicts 4.6 million will ship in 1999 compared to 27.4 million CD ROMs. Has been ratified by the DVD Forum as an acceptable format for the mass market. DVD RAM Vendors are very excited about the possibilities of this format. Both Hitachi and Toshiba are shipping drives. Currently priced at around £500, analysts predict prices will eventually fall to around £200. Able to store 2.6GB per side and upgraded to 4.7GB per side by the end of the year, 4,000 units have shipped in Europe so far and analyst predict total RAM shipments of 60,000 in 1999. Ratified by the DVD Forum. DVD + RW Primarily with only Sony behind it, some industry commentators accuse the format of being a distraction in the market. It has not been ratified by the DVD Forum, and is effectively a direct competitor to DVD RAM. "They felt it didn't add anything more to the other formats," said Franco de Bonis of Creative. DVD-RW The dark horse of the formats. A rewriteable standard like DVD RAM, it looks to be very expensive and the specification for the technology is not yet know. "The jury is still out on that one," said de Bonis. DVD R A write-once standard with limited applications, unlikely to be economic for end users. Useful for organisations which do a lot of archiving or need to store huge amounts of data that won't need to be altered. Possibly useful for games developers. Currently drives are prohibitively expensive at around £5000. Take me to the DVD Basement.