Western Digital,a leading maker of computer hard drives agreed to buy SanDisk,which makes "flash" memory chips used in snartphones and tablets,for $19 billion in cash and shares.Western Digital's sales fell last year,reflecting the shift to mobile computing;SanDisk has also stumbled stumbled lately,making it a takeover target as the chip industry consolidates. flash memory:閃存 mobile computing:移動計算 stumble:發(fā)展不順 takeover target:收購標(biāo)的 chip:芯片 consolidate:整合