This Christmas, thousands of homes will be filled with the sound of beeps, crashes, bangs and roars as children unwrap and play the latest computer games. The computer games industry believes we will spend some pound;720 million on games this year, representing 85 per cent of the leisure software market. The remaining 15 per cent includes educational software.

With so much time and money spent on computer games, it’s little wonder that today’s youngsters are known in the trade as “screenagers”, and many of them handle their games controller pads with the dexterity of a touch-typist.

There are two types of games machines: consoles and desktop computers. Consoles are dedicated games machines that plug into a home television. The market is dominated by Sony’s PlayStation, which has sold six million units in the UK, and Nintendo’s N64, which has sales of 1.5 million. Both these consoles are several years old (ancient in the fast-moving world of computer games) and can now be bought for pound;70 to pound;80 each. Many stores offer deals that bundle a game with the console and most games now cost around pound;35 each. These price reductions have also occurred because there is a new player in town - Sega’s Dreamcast console.

Sega’s last console, the Saturn, flopped, but it has high hopes for Dreamcast. Computer games systems are measured in bits and as a rule of thumb the higher the bit number, the faster the games machine and the better the graphics. PlayStation is a 32-bit system; N64 is 64-bit; but Dreamcast is a 128-bit machine. Sega says Dreamcast is 15 times more powerful than a PlayStation, 10 times more powerful than an N64 and has four times the graphics processing power of the fastest Pentium II chip used in many home PCs. All of which means the Dreamcast is the closest thing to an arcade games machine.

Dreamcast is also the first games console to offer Internet access via the television. It has a built-in modem and Web browser and Sega and BT have launched a free Internet service (although there are call charges). As a result, users will be able to send and receive emails, explore the Internet and play against other Dreamcast owners around the country.

There will be about 40 Dreamcast games available in time for Christmas, each costing around pound;40. Among Sega’s offerings is Sega Rally 2, an amazing racing game, and the return of that super-charged hedgehog Sonic in Sonic Adventure. Infogrames’ UEFA Striker is one of the best football games I have seen. It not only boasts superb animation, it lets users select their team, decide on a formation and pick tactics.

Younger children will have lots of fun with Infogrames’ Pen Pen, which involves cartoon penguins in all kinds of games. Perhaps not every parent will approve of Midway’s Ready 2 Rumble boxing game, but the graphics are excellent and the characters are more humorous than menacing. Maybe they will be more approving of Midway’s basketball game, NBA Showtime. Another games outfit, Acclaim, has you zipping around on a hoverboard - a sort of glorified skateboard - in TrickStyle, or for more cerebral gaming Eidos offers Power Stone, an adventure set in the 19th century.

In a bid to square up to this newcomer, next year Sony and Nintendo launch more powerful consoles. Sony’s PlayStation 2 will play existing PlayStation titles and DVD video discs as well as new PlayStation 2 disks. It will also offer ways of linking up to a computer network like the Internet. Nintendo’s new console, code-named Dolphin, is due to arrive around autumn 2000. Even Microsoft is developing a new console, code-named the X-Box, which is said to be as powerful as PlayStation 2.

Yet while a flurry of games is appearing for consoles, most are developed for the PC and then transferred to console systems like PlayStation. As computer games become more sophisticated, evermore powerful PCs are required to play them. The minimum requirement for the latest games is a PC with 64 megabytes of memory (although 128 megabytes is often recommended), a fast Pentium chip and a hard drive of at least 10 gigabytes. And many games will only work if your PC has a special 3-D graphics card for fast-moving animation. In the same way, many games offer surround-sound effects, and companies such as Creative Technology market surround-sound kits for PCs.

Historically, far fewer games have been produced for Apple Macs, but the launch of iMac has revitalised the Apple software industry, a move helped by the powerful graphics capabilities and hi-fi sound of the new Macs. What’s more, owners of the latest Apple computers can use software like SoftWindows and Virtual PC that allows them to play PC games on an Apple machine.