In 1972, engineers at Hewlett-Packard rose to a challenge from founder William Hewlett to fit all the scientific functions of the company's flagship desktop calculator into something he could slip into his shirt pocket. They came up with the HP-35, a scientific calculator no bigger than a box of Milk Duds -- and arguably the world's first handheld computer.
Join us for a tour of 15 of the most notable handheld computers from the past 40 years. Some were wildly successful, others infamous flops, but they were all commercially available products, not concepts or prototypes. And they could all be held in one hand and operated with the other -- no laptops, netbooks or laptop/tablet hybrids allowed in our list.