A user interface, or user interface( UI), is the way commands and data are entered into the computer. The user interface is the interface between the computer and the human being. It is provided by the operating system or application programs and is designed to make it easier for the user to work with the computer.
With the continuous development of personal computers(PCs) and the rapid increase in computing power, the user interfaces of PCs have also evolved, moving from the simple command line interface( CLI) to text-based input platforms to intuitive user interfaces controlled by fingers, gestures or speech.
The first user interfaces operated text-based. This simple user interface, as used in the DOS operating system, was the text-based Character User Interface( CUI). Input was via text input or key combinations, which either had to be laboriously learned or read from long tables. The most commonly used user interfaces are the keyboard and mouse, others are the touchscreen, multi-touchscreen and touchpad.
The graphical user interfaces( GUI) followed, where instead of cryptic commands, icons, menus, menu bars, buttons, pictograms and symbols are available for function input and program selection, whose activation is done using the mouse, function keys or key combinations. Dialog boxes are available for interaction. The graphical user interfaces (GUI) are designed in such a way that situation-related nonsensical commands are not executed or are not even offered. Further development leads to user interfaces such as those used by game consoles and multi-touch displays, to voice-controlled user interfaces, the Voice User Interfaces(VUI), the voice browsers and those with voice control such as the Conversational User Interfaces (CUI) and last but not least to the Natural User Interfaces( NUI), which are controlled by speech, gestures or facial expressions.
In addition to the aforementioned user interfaces, there are barrier-free user interfaces for the speech- and visually-impaired, and for people with motor and cognitive disorders. Furthermore, there are brain-computer interfaces( BCI) that are controlled by brain waves.