Remember life without your iPhone, Blackberry or Treo? A look at the evolution of the personal digital assistant.

Personal digital assistants, or PDAs, have come a long way since Palm's Jeff Hawkins used a block of wood and imitation stylus (right) as a model during the development of the first Palm Pilot, in 1996. Early competition among companies to be first with a breakthrough device has given way to spectacular advances. Today's models are also cell phones, satellite-coordinated maps, game consoles, and can store many thousands of times the data of their predecessors, enough for whole music and movie collections. Now PDAs are ubiquitous, to the point that it's not at all uncommon to see someone carrying two -- one for personal use, one issued by an employer.