The next generation of personal computers and portable music players could hold 10 times more information than current models, thanks to a different way of writing magnetic data to a hard disc.

Japanese electronics company Hitachi announced on Monday that a number of its employees had begun testing the experimental technology, known as "perpendicular recording". The company aims to offer drives incorporating it to the public towards the end of 2005.

Hard drives store information by magnetising sectors of a disc in a specific direction, which then correspond to either a “1” or a “0”. This is done by passing magnetic heads over the disc surface which magnetises the sectors in a direction parallel to its surface - so-called "longitudinal recording". The heads are turned around to impart the reverse polarity.

Perpendicular recording uses different-shaped heads to magnetise disc sectors so that the polarity points either up or down - at 90° to the disc’s surface. Data can still be retrieved from the disc in the traditional way, using another head to detect the magnetic charge.

"It's a major technical change," says John Fox, business manager for Hitachi's European hard drive business. "But it's transparent to the user."