Operating systems

A feature is one of the four WIMP building blocks — a window, an icon, a menu or the pointer. A benefit is a reason the GUI helps the user: easy for a beginner, no commands to memorise, icons recognisable without reading text. Asked to state a feature, answer Window / Icon / Menu / Pointer only; a benefit scores nothing there, and the reverse is equally true.

Asked for a drawback of a dialogue-based (voice) interface, candidates say why it is good instead. Hands-free operation, use while driving, and help for a user with limited mobility or a visual impairment are all advantages — none can score on a drawback question. A drawback must be something the interface does badly: a misheard command, or being overheard in public.

Not just "it does not always understand" — name the CAUSE: background noise, an unfamiliar accent or dialect, or an unclear, quiet voice. Not just "it is not private" — explain that a spoken command can be overheard in a public place, unlike typing or clicking silently. A drawback with no cause or consequence attached is treated as no answer.

Gesture-based interfaces are a newer topic, and candidates answer "gestures are used to control it using gestures" — repeating the stem adds no information and is never credited. Say what moves (a hand, a finger or the whole body), what detects it (a touchscreen, sensor or camera), and what the movement makes the device do.

Three drawbacks are credited. Accuracy — the sensor or camera misreads a movement, so the wrong action happens. Limited gesture set — only a small, fixed list of gestures is recognised, so an unusual movement means nothing. Accessibility — a user with restricted movement may be unable to perform the required gesture at all, making the device unusable for them.

A benefit states something good on its own; an advantage compares with the alternative the question names. "Icons are pictures" is a fact; "a GUI is quicker to learn than a CLI" is an advantage. Any advantage, disadvantage, compare or discuss answer needs a comparative word — quicker, easier, more accurate — or it is read as a one-sided statement and scores nothing.

Both are hands-free and neither needs a keyboard or mouse, which is why they get swapped. Dialogue-based takes spoken input, read by speech-recognition software. Gesture-based takes a movement — a swipe, pinch or wave — detected by a touchscreen, sensor or camera. Noise and accent are voice drawbacks; a limited, fixed gesture set belongs to gesture.