interface
interface
English/French
“The surface where two systems meet is an interface — and the concept that a complex system should hide its complexity behind a well-designed boundary is the design principle that made computers usable by anyone who was not an engineer.”
Interface was first used in physics and chemistry in the 1880s: the interface between two liquids (the surface where oil and water meet), the interface between a solid and a gas. Inter- (between) plus face (surface, from Latin facies) gave a word for the meeting surface between two distinct systems. The term was descriptive and neutral — the boundary itself, neither one system nor the other.
Computing adopted interface in the 1960s to mean the connection point between components: the hardware interface between a computer and a printer, the software interface between an operating system and an application program. An interface defined the rules of communication between two systems without specifying what either system did internally. The interface was the contract.
The user interface (UI) — the visible surface through which humans interact with computers — emerged as a concept at Xerox PARC in the 1970s. Douglas Engelbart had demonstrated mouse-driven graphical interaction in 1968; PARC researchers built the Alto computer with a graphical desktop environment in 1973. Apple visited PARC in 1979, hired PARC researchers, and shipped the Macintosh in 1984 — the first mass-market computer with a graphical user interface. The interface was now a designed thing.
Steve Jobs's contribution was treating the user interface as a primary design problem, not an engineering afterthought. The Mac's font-based menus, overlapping windows, and click-to-point mouse paradigm hid enormous complexity behind a simple surface. The interface was the product. Don Norman's The Design of Everyday Things (1988) popularized the principles: affordances, feedback, visibility. The word interface moved from physics to design philosophy.
Related Words
Today
The interface is the lie that makes computing possible. Behind the icon, the click, the menu — there is binary code operating at nanosecond speeds in a language no human reads naturally. The interface hides all of that and presents a surface of drawers, folders, trash cans, desktops.
The design choice to call the computer's surface a 'desktop' — with files and folders and a trash can — was not just metaphor. It was an act of usability. The physics word for the boundary between two substances became the design word for the boundary between machine complexity and human comprehension.
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