It is necessary to de”ne a PDA before we can discuss its history or how it is used in the workplace or as a personal computing device. If we do not have a common de”nition or understanding of something, then it is not possible to discuss it. As you progress through the discipline of eforensics, you will ”nd that it will serve you well to learn some common de”nitions of devices, tools, and legal concepts. It is also good to learn a brief history of each device, who invented it, what operating systems a device uses, and some tools to examine it.