The mouse

December 2016

Introduction to the mouse

The mouse is a pointing device used to move a cursor on the screen and allowing objects to be selected, moved and manipulated using the buttons. The consistent action of pressing (clicking) on a button in order to carry out an action is called a "click".

The first mouse was invented and developed by Douglas Carle Engelbart of the Stanford Research Institute (SRI): it was a wooden mouse containing two perpendicular discs and connected to the computer by a pair of twisted wires.

Mouse connector

The mouse is generally plugged in to the back of the central processing unit, into the motherboard, with a green PS/2 connector:

PS/2 connector

Some mice, with advanced functionalities sometimes have a USB connector.

Types of mice

There are several types of mice, classified according to the positioning technology on the one hand and the data transmission to the central processing unit on the other.

We can therefore distinguish several large categories of mice:

  • Mechanical mice, where the operation is based on a ball (in plastic or rubber) encased in a frame (in plastic) transmitting the movement to two rollers;
  • Optical-mechanical mice, where the operation is similar to that of mechanical mice, except the movement of the ball is detected by optic sensors.
  • Optical mice, capable of determining movement through visual analysis of the surface upon which they slide.

Mechanical mouse

The mechanical mouse comprises of a ball upon which two rollers turn. These rollers each comprise of a notched disc which turns between a photodiode and LED (Light Emitting Diode) allowing the light to pass through in sequence. When the light passes through, the photodiode sends a bit (1), when it meets an obstacle, the photodiode sends a zero bit (0). Using this information, the computer knows the position of the cursor and even its speed.

Inside of a mouse

Tip: As you use it, dust settles on the mouse rollers preventing them from turning correctly and causing strange reactions in the cursor. To remedy this, simply open the cage containing the ball and clean the rollers (with a toothbrush for example).

Optical mouse

The optical mouse operates by analysing the surface on which it moves. So, an optical mouse is comprised of an LED, an image acquisition system (IAS) and a digital signal processor (DSP).

The LED is responsible for shining on the surface so as to enable the IAS to get an image of the surface. The DSP, through analysing the microscopic characteristics of the surface determines the horizontal and vertical movement.

Optical mice operate on any slightly uneven or even colored surface. The main advantages of this type of pointing device in comparison to the mechanical mouse are greater precision along with less dirtiness.

Cordless mouse

Cordless mice are more and more popular because they can be used without physically being connected to the computer, which gives a sensation of freedom.

There are also several categories of cordless mice, depending on the technology used:

  • Infrared mouse (IR) these mice are used with an infrared receiver connected to the computer. The range of this type of device is a few metres at most with direct line of sight in the same way as a television remote.
  • Hertzian mouse: these mice are used with a hertzian receiver, generally proprietary to the manufacturer. The range of this type of device is around ten metres at most, not necessarily with direct line of sight to the computer. This type of device can be practical for people connecting their computer to their television in another room.
  • Bluetooth mouse: these mice are used with a Bluetooth receiver connected to the computer. The range of this type of device is the same as the propriety hertzian technologies.

Mouse wheel

Mice are increasingly equipped with a wheel. The wheel, generally located between the right and left buttons makes it possible to scroll through pages while enabling the user to move the cursor on the screen.


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