A computer mouse is an input device that is most often used with a personal computer. Moving a mouse along a flat surface can move the on-screen cursor to different items on the screen. Items can be moved or selected by pressing the mouse buttons (called clicking). It is called a computer mouse because of the wire that connects the mouse to the computer. The people who designed the first computer mice thought that it looked like the tail on a mouse. Today, many computer mice use wireless technology and have no wire.

In 1964 Douglas Engelbart (1925-2013), a researcher at Stanford Research Institute, wanted to find a way to make using computers easier. In those days, computers were large and expensive. Using them was very hard because everything had to be typed in by hand, and there was no way to alter things if you made a mistake. After studying and designing for a long time, Engelbart succeeded in inventing an input device which he named ‘XY index’. At first, it needed two hands to use, but it was changed so that only one hand was needed to use it. This model was more like the mouse that we use today. Xerox Palo Alto Research introduced a GUI in 1981, using a mouse. The mouse was used with Macintosh of Apple Inc. when it came out in 1984. Microsoft Windows also used the mouse when it came out, so over time computer mice became used with many computers. Modern mice have three buttons: left button, right button, scroll button.

A mouse typically controls the motion of a pointer in two dimensions in a graphical user interface (GUI). The mouse turns movements of the hand backward and forward, left and right into equivalent electronic signals that in turn are used to move the pointer.

The relative movements of the mouse on the surface are applied to the position of the pointer on the screen, which signals the point where actions of the user take place, so hand movements are replicated by the pointer. Clicking or hovering (stopping movement while the cursor is within the bounds of an area) can select files, programs or actions from a list of names, or (in graphical interfaces) through small images called “icons” and other elements. For example, a text file might be represented by a picture of a paper notebook and clicking while the cursor hovers this icon might cause a text editing program to open the file in a window.

Different ways of operating the mouse cause specific things to happen in the GUI:

  • Click: pressing and releasing a button.
    • (left) Single-click: clicking the main button.
    • (left) Double-click: clicking the button two times in quick succession counts as a different gesture than two separate single clicks.
    • (left) Triple-click: clicking the button three times in quick succession counts as a different gesture than three separate single clicks. Triple clicks are far less common in traditional navigation.
    • Right-click: clicking the secondary button, or clicking with two fingers. (This brings a menu with different options depending on the software)
    • Middle-click: clicking the tertiary button.
  • Drag and drop: pressing and holding a button, then moving the mouse without releasing. (Using the command “drag with the right mouse button” instead of just “drag” when one instructs a user to drag an object while holding the right mouse button down instead of the more commonly used left mouse button.)
  • Mouse button chording (a.k.a. Rocker navigation).
    • Combination of right-click then left-click.
    • Combination of left-click then right-click or keyboard letter.
    • Combination of left or right-click and the mouse wheel.
  • Clicking while holding down a modifier key.
  • Moving the pointer a long distance: When a practical limit of mouse movement is reached, one lifts up the mouse, brings it to the opposite edge of the working area while it is held above the surface, and then replaces it down onto the working surface. This is often not necessary, because acceleration software detects fast movement, and moves the pointer significantly faster in proportion than for slow mouse motion.
  • Multi-touch: this method is similar to a multi-touch trackpad on a laptop with support for tap input for multiple fingers, the most famous example being the Apple Magic Mouse.