A leading indicator of the semiconductor industry, the book-to-bill ratio, reversed course last month and rose after four straight months of decline, the Semiconductor Industry Assn. reported. The October ratio, reflecting a seasonal upturn after the traditional summer slowdown for computer chip makers, rose to 1.06 from 1.04 in September, the association said. October's book-to-bill ratio means that for every $100 worth of shipments made during the month, the suppliers took in $106 of orders. The industry association also revised the August ratio from 1.06 to 1.09.