A mobile device is a small, hand-held computing device, typically having a display screen with touch

Touchscreen

A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touchscreens can also sense other passive objects, such as a stylus...

 input and/or a miniature keyboard and less than 2 lbs. Early pocket sized ones were joined in the late 2000s by larger but otherwise similar tablet computer

Tablet computer

A tablet computer, or simply tablet, is a complete mobile computer, larger than a mobile phone or personal digital assistant, integrated into a flat touch screen and primarily operated by touching the screen...

s. As in a personal digital assistant

Personal digital assistant

A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...

 (PDA), the input and output are often combined into a touch-screen interface

Interface (computer science)

In the field of computer science, an interface is a tool and concept that refers to a point of interaction between components, and is applicable at the level of both hardware and software...

.

Smartphone

Smartphone

A smartphone is a high-end mobile phone built on a mobile computing platform, with more advanced computing ability and connectivity than a contemporary feature phone. The first smartphones were devices that mainly combined the functions of a personal digital assistant and a mobile phone or camera...

s and PDAs are popular amongst those who wish to use some of the powers of a conventional computer, in environments where carrying one would not be practical.