Scroll wheel

The wheel is often, but not always, engineered with detents to turn in discrete steps, rather than continuously as an analog axis, to allow the operator to more easily intuit how far they are scrolling.

Some user interfaces, like Cinnamon (desktop environment), allow using it to adjust brightness and volume by pointing at the respective taskbar icon while scrolling.

The earliest known example of the former is the Mighty Mouse prototype developed jointly by NTT, Japan and ETH Zürich, Switzerland (Kunio Ōno, Ken'ichi Fukaya and Jürg Nievergelt) in 1985.

[5] At the ACM SIGCHI conference in 1989, Gina Danielle Venolia from Apple presented a mouse prototype with a horizontal thumb-wheel for scrolling, or for navigating inwards and outwards: zooming or along the third axis in 3D space.

[7][11] Scroll wheels can also be found on PDAs and mobiles phones such as early Sony models, BlackBerry devices and Nokia 7110, which usually have the function of navigating through menus.

In mice, alternatives include scroll balls (similar to trackballs, such as on Apple's Mighty Mouse and some serial or PS/2 mice, which combine horizontal and vertical scrolling), pointing sticks,[14] integrated touchpads (as on Apple's Magic Mouse) or optical sensors.

Genius also offered the simpler NetMouse in the late 1990s, which had a two-way rocker switch instead of a wheel, marketed as the Magic Scroll Button.

[22] This has become a de facto standard in many 3D applications, with Trimble's SketchUp (formerly owned by Google) using the scroll wheel to zoom in and out in the 3D space, while a wheel-click and a mouse drag is orbit.