Apple also tends to re-focus on product lines and push the boundaries even further. And each product set relies on the other to drag itself forward. Look at how the latest OS X Yosemite has borrowed heavily from iOS and vice versa. In October Apple revealed its new iMac Retina 5k display, proving there's plenty of life in the desktop yet. In Q4 Apple sold 5.5m Mac computers, straddling ultra portable MacBook Air devices to sturdy MacBook Pro and iMac desktop products.