Certified IT Support Professional Learning Resources Mouse Basics

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Mouse Basics

In computing, a mouse is a pointing device that functions by detecting two-dimensional motion relative to its supporting surface. Physically, a mouse consists of an object held under one of the user's hands, with one or more buttons.

The mouse sometimes features other elements, such as "wheels", which allow the user to perform various system-dependent operations, or extra buttons or features that can add more control or dimensional input. The mouse's motion typically translates into the motion of a pointer on a display, which allows for fine control of a graphical user interface.

The original optical-mouse technology bounced a focused beam of light off a highly-reflective mouse pad onto a sensor. The mouse pad had a grid of dark lines. Each time the mouse was moved, the beam of light was interrupted by the grid. Whenever the light was interrupted, the sensor sent a signal to the computer and the cursor moved a corresponding amount.

This kind of optical mouse was difficult to use, requiring that you hold it at precisely the right angle to ensure that the light beam and sensor aligned. Also, damage to or loss of the mouse pad rendered the mouse useless until a replacement pad was purchased. Today's optical mice are far more user-friendly and reliable.

Developed by Agilent Technologies and introduced to the world in late 1999, the optical mouse­ actually uses a tiny camera to take thousands of pictures every second.

Able to work on almost any surface without a mouse pad, most optical mice use a small, red light-emitting diode (LED) that bounces light off that surface onto a complimentary metal-oxide semiconductor (CMOS) sensor. In addition to LEDs, a recent innovation are laser-based optical mice that detect more surface details compared to LED technology. This results in the ability to use a laser-based optical mouse on even more surfaces than an LED mouse.

Here's how the sensor and other parts of an optical mouse work together:

  • The CMOS sensor sends each image to a digital signal processor (DSP) for analysis.
  • The DSP detects patterns in the images and examines how the patterns have moved since the previous image.
  • Based on the change in patterns over a sequence of images, the DSP determines how far the mouse has moved and sends the corresponding coordinates to the computer.
  • The computer moves the cursor on the screen based on the coordinates received from the mouse. This happens hundreds of times each second, making the cursor appear to move very smoothly.


  • Optical mice have several benefits over track-ball mice:
  • No moving parts means less wear and a lower chance of failure.
  • There's no way for dirt to get inside the mouse and interfere with the tracking sensors.
  • Increased tracking resolution means a smoother response.
  • They don't require a special surface, such as a mouse pad.

The Pointer
The pointer allows you to interact and operate the graphical user interface.

The pointer is the indicator on the screen that shows the current location for mouse activities. When you move the mouse on the mouse pad, the pointer moves on the screen. The pointer shape is the shape of an arrow.

The Mouse Buttons
Left Button or SELECT -     SELECT Button Selects items on pop-up windows, chooses default menu items, and selects GUI items.

Middle Button or SCROLL -     SCROLL Button The scroll button is used to move lengthy page up or down in the GUI.

Right Button or MENU -    MENU Button Displays menus, submenus, and pop-up menus, and chooses items from menus.

Mouse Button Activities
Standard mouse button activities are clicking, pressing, and dragging.

Click -     Press and release the designated mouse button quickly. To "double-click," press and release the designated mouse button twice quickly.
Press -     Press and hold down the designated mouse button.
Drag -     Press the designated mouse button, hold it down while moving the mouse, then release the button.

The names of the buttons (SELECT, ADJUST, and MENU) and the kinds of mouse activities (click, press, and drag) will be used throughout other parts of the help system.

An image of optical mouse -


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