Here's to the next billion...Personal computer number one billion has just been sold, according a study by analyst group Gartner. Over the last quarter of a century, 75 per cent of PCs made have been sold into the workplace and 25 per cent for personal or home use. Gartner predicts it will take a fraction of the time to reach the next billion, estimating that PC shipments will double as early as 2007. The commercial PC dates back to the introduction of the Altair 8800 in 1975. It wasn't until the introduction of the IBM PC - and its copycats - running Microsoft's disk operating system (MS-DOS) in the early 1980s, however, that sales of personal computers began to grow significantly. The Gartner report reveals that the US is the biggest consumer of PC technology, accounting for 38.8 per cent of all machines sold. Europe accounts for around 25 per cent with just fewer than 12 per cent going to Asia-Pacific. The billionth PC was probably sold in April, the Gartner study says. PC shipments declined last year for only the second time in the history of the technology.