US sales of personal computer software soared 50.3% in the second quarter of 1988, according to the Software Publishers Association. The group reckons sales in North America totalled $922m in the period, up from $614m a year earlier – and confirmation of Apple Computer’s Macintosh as a true business alternative to the MS-DOS standard comes with the news that sales of software for the Macintosh was the fastest-growing segment in the half, rising 179% to $109m – still a ways behind the business done in MS-DOS software, up 40.8% to $702m. Going in th eother direction, Apple II software sales fell 5.4% to $37m and Commodore 64 and 128 software sales slipped 10.6% to $20.6m. Overall software sales for the first half rose 50.5% to $1,820m. The report is based on confidential sales figures submitted voluntarily to accountants Arthur Andersen & Co by most major companies in each market segment. Sales for smaller firms are estimated.