Graphical User Interface

A graphical user interface, or GUI, is the visual layer a person interacts with. In chess it can display the chessboard, move list, clocks, buttons, and analysis panels. Its main job is to make the work of other software components visible and easy to control.

The GUI does not have to be the program calculating the best moves. That work can be performed by a chess engine, a program specialized in analyzing positions. Stockfish, for example, is an engine that can operate through text commands and does not include its own GUI. A graphical application can connect to it and present its output in a readable form.

A common way for a GUI and engine to communicate is UCI, short for Universal Chess Interface. UCI is a text protocol: it defines messages for setting a position, requesting analysis, and receiving results. The GUI can turn that technical output into displays such as a principal variation, the move sequence the engine currently considers best, an evaluation of which side it considers better, or the reported depth, an indicator of search progress. It may run a local engine, which calculates on the user's device, or connect to a cloud engine, which calculates on a remote computer.