In Motif terminology, any reaction of the interface to a user input is called an action.

In programming for the X Window System, a callback is a procedure that gets called when some event, such as button click, takes place. Essentially the use interface is calling the application back for service.

A computer language that can function as an embedded interpreter. For example, the Tcl language is embedded as the tool control language of applications written in Tk or Tm. Tcl could also be embedded in applications running on Microsoft Windows^™ or other systems. To be embeddable, a language must be relatively simple (unlike C++) and stand by itself (unlike the Bourne shell, which requires commands).

A relatively small language interpreter embedded in another system. One example is the Lisp interpreter embedded in emacs.

Hardware and software that forms a component of some larger system and is expected to function without human intervention. Typically an embedded system consists of a single-board microcomputer with software in ROM, which starts running a dedicated application as soon as power is turned on and does not stop until power is turned off.

In Motif terminology, any user input having a symbolic name is called an event.

Acronym for graphical user interface: a software system that relies on tactile metaphors such as the push-button and picture icon to encapsulate commands issued by a person to the computer.

In X Window System terminology, a keysym is an abstract label for a keyboard symbol, often matching the engraving on the key.

In Motif terminology, a sash is the small handle on a pane separator that allows the user to change the space alloted for each widget. Enhanced Motif permits sashes to operate in both directions, but standard Motif works only for horizontal pane separators.

In Xt and Motif, visual objects on the screen that can be manupulated with the mouse and keyboard.