Editing Computer mouse (section)

== Speed ==
[[Mickey (unit)|Mickeys]] per second is a unit of measurement for the speed and movement direction of a computer mouse,<ref name="int33h" /> where direction is often expressed as "horizontal" versus "vertical" mickey count. However, speed can also refer to the ratio between how many pixels the cursor moves on the screen and how far the mouse moves on the mouse pad, which may be expressed as [[pixels]] per mickey, pixels per [[inch]], or pixels per [[centimeter]].

The computer industry often measures mouse sensitivity in terms of counts per inch (CPI), commonly expressed as dots per inch (DPI){{spaced en dash}}the number of steps the mouse will report when it moves one inch. In early mice, this specification was called pulses per inch (ppi).<ref name="hawley" /> The mickey originally referred to one of these counts, or one resolvable step of motion. If the default mouse-tracking condition involves moving the cursor by one screen-pixel or dot on-screen per reported step, then the CPI does equate to DPI: dots of cursor motion per inch of mouse motion. The CPI or DPI as reported by manufacturers depends on how they make the mouse; the higher the CPI, the faster the cursor moves with mouse movement. However, operating system and application software can adjust the mouse sensitivity, making the cursor move faster or slower than its CPI. {{As of|2007|post=,}} software can change the speed of the cursor dynamically, taking into account the mouse's absolute speed and the movement from the last stop-point.<ref>{{Cite journal |last=Müller |first=Jörg |date=26 Feb 2018 |title=Dynamics of Pointing with Pointer Acceleration |url=https://inria.hal.science/hal-01717219/document |journal=IFIP Conference on Human-Computer Interaction  |pages=475–495 |quote=[Pointer acceleration] functions increase the mouse gain with increasing mouse velocity. |via=HAL}}</ref>

For simple software, when the mouse starts to move, the software will count the number of "counts" or "mickeys" received from the mouse and will move the cursor across the screen by that number of pixels (or multiplied by a rate factor, typically less than 1). The cursor will move slowly on the screen, with good precision. When the movement of the mouse passes the value set for some threshold, the software will start to move the cursor faster, with a greater rate factor. Usually, the user can set the value of the second rate factor by changing the "acceleration" setting.

Operating systems sometimes apply acceleration, referred to as "[[ballistics]]", to the motion reported by the mouse. For example, versions of [[Microsoft Windows|Windows]] prior to [[Windows XP]] doubled reported values above a configurable threshold, and then optionally doubled them again above a second configurable threshold. These doublings applied separately in the X and Y directions, resulting in very [[nonlinear system|nonlinear]] response.<ref>{{cite web |url=http://www.microsoft.com/whdc/archive/pointer-bal.mspx |title=Pointer ballistics for Windows XP |date=2002 |work=Windows Hardware Developer Center Archive |publisher=[[Microsoft]] |access-date=2010-04-29 |url-status=dead |archive-url=https://web.archive.org/web/20101222190833/http://www.microsoft.com/whdc/archive/pointer-bal.mspx |archive-date=2010-12-22}}</ref>