Apple and IBM were bitter enemies during the early PC era, but what would have been unthinkable 30 years ago, has happened: the two are now teaming up. The companies yesterday announced a partnership to build enterprise applications for iPads and iPhones and sell iOS devices to Big Blue's corporate customers.

"In '84, we were competitors. In 2014, I don't think you can find two more complementary companies", said Apple's CEO Tim Cook, who worked at IBM for more than 10 years prior to joining Apple, in a joint interview with IBM CEO Virginia Rometty. "This is a really landmark deal".

The idea behind the alliance, which was six months in the making, is to combine strengths -- Apple's expertise in consumer devices and IBM's reputation and relationship with the corporate world. Both the companies will work together to develop applications that will draw on IBM computing services such as device management, security, and big-data analytics.

Apple has never been an enterprise company. Although it has made some inroads in this segment with Tim Cook at the helm, the partnership will help the iPhone-maker capture a bigger slice of the enterprise market.

On the other hand, IBM is hoping that the partnership will not only help stem eight consecutive quarters of year-over-year revenue declines, it will also give the company a premium advantage in the race for mobile enterprise leadership.

Under the agreement, a new AppleCare-like service for enterprise will also be setup, providing on-site support and service delivered by IBM.

Engineers from both companies are working together to develop more than 100 apps for various markets including retail, healthcare, banking, travel, telecom, transportation, insurance, and more. The first set of apps will arrive this fall.