The phrase "mobile computing" generally refers to the ability to use a computing device in transit. Since the 1900s, mobile computers have taken the form of a wearable computer, personal digital assistant, smartphone, carputer, and UMPC. This category is dedicated to the technology or computing devices that can be operated as the user moves, as opposed to portable computers--though they can be easily be moved from one place to another--that necessitate time for setting up and usually running on AC power.