Manufacturers are devising ways of combining Internet services with the power of CD-Rom to give users the best of both technologies. Steve Homer explains
The Internet or other online services may well, one day, put paid to CD-Rom: we will download what we need or fancy, and play it when we want to. But for now, the Internet is an also-ran to the CD in multimedia. Downloading moving images, be they animation, computer graphics or TV- quality video, is not an option for anyone with less than an hour to spend waiting for 30 seconds of images to arrive.

Several companies have, however, seen a way of combining the two technologies to give the best of both worlds: the size and timeliness of online databases with the quality of CD-Rom. CompuServe, the biggest online service, has a quarterly subscription CD-Rom. On the disk are film and audio clips - tasters to information online. If you find something you like, one click takes you to the appropriate online site.

An even more ambitious project is Philips's new CD Online service. This uses Philips's CD-i player, which plays through the television, as a platform to access the World Wide Web. The company has its own site on the Web that cleverly links data on the disk with information stored on the server. For example, at Christmas, messages sent from the central computer will be mixed with images and audio stored on the disk to create an electronic advent calendar that will be displayed on the television.

The advantage of this dual approach is particularly apparent with the CD-i machine. With proper VHS-quality video clips stored on the CD-i disk, it makes the information delivered over the modem look really good.

Hybrid CDs are becoming more and more common. Microsoft now has half a dozen disks that take small amounts of information off the Internet to add to its titles. One of the first was a baseball title that allowed fans to log on and see the latest league scores.

Microsoft is extending this approach. Monthly updates are available for its Encarta encyclopaedia, as are the latest reviews for its movie guide, Cinemania and its music guide, Music Central.

This is not an entirely altruistic exercise. Encarta's updates integrate only into the current version, which is replaced every autumn. To have a fully integrated encyclopaedia, therefore, you have to buy a new disk every year.

At pounds 50 this is is good value - but you might like to think of it as an annual subscription rather than an outright purchase price.