1) I do not exactly understand the question. A handheld computer is a device, which offers various output possibilities. Normal output is the screen display, but you could connect it to various peripherals such as a printer, or to the internet. The other items that you list are images or documents, which could be stored and also processed on a computer, and you could output them in a particular form (print, screen or projection display, etc) 2) "A mobile device (also known as converged device, handheld device, handheld computer, "Palmtop" or simply handheld) is a pocket-sized computing device, typically having a display screen with touch input or a miniature keyboard. In the case of the personal digital assistant (PDA) the input and output are combined into a touch-screen interface. Smartphones and PDAs are popular amongst those who require the assistance and convenience of a conventional computer, in environments where carrying one would not be practical. Enterprise digital assistants can further extend the available functionality for the business user by offering integrated data capture devices like Bar Code, RFID and Smart Card readers." "Most handhelds can be used to send and receive faxes by email using an Internet fax service. Internet faxing also enables handheld users to print documents by sending them to a nearby fax machine. This service is available through most internet fax providers." "Mobile devices have wireless capability to connect to the Internet and office/home computer systems." Source and further information: http://en.wikipedia.org/wiki/Mobile_device 3) "The user interface (or Human Machine Interface) is the aggregate of means by which people—the users—interact with the system—a particular machine, device, computer program or other complex tools. The user interface provides means of: Input, allowing the users to manipulate a system Output, allowing the system to produce the effects of the users' manipulation." Source and further information: http://en.wikipedia.org/wiki/User_interface