In computer science and human-computer interaction, the Human-Machine Interface (HMI) refers to the graphical, textual and auditory information the program presents to the user (operator) using computer monitors and audio subsystems, and the control sequences (such as keystrokes with the computer keyboard, movements of the computer mouse, and selections with the touchscreen) the user employs to control the program. Currently the following types of HMI are the most common:
- Graphical user interfaces(GUI) accept input via devices such as computer keyboard and mouse and provide articulated graphical output on the computer monitor.
- Web-based user interfaces accept input and provide output by generating web pages which are transported via the network and viewed by the user using a web browser program.
The operations user must be able to control the system and assess the state of the system. Each control system vendor provides a unique look-and-feel to their basic HMI applications. An older, not gender-neutral version of the term is man-machine interface (MMI).
The system may expose several user interfaces to serve different kinds of users. User interface screens may be optimized to provide the appropriate information and control interface to operations users, engineering users and management users.