Phil Storrs PC Hardware book

Mouse input devices

Computer mouse devices fall into two basic categories

Mechanical Mice

The Mechanical Mouse is by far the most popular in use and here is how it works.


The Mechanical Mouse on the left uses mechanical contacts on the encoder wheels, the Mouse on the right uses optical encoders. The left hand Mouse is a chordless device and uses an Infrared link back to a charging station. Note the Battery in this device.

The Optical Mouse

Note the special Mouse Mat for an optical mouse

The Mouse Interface

The interface between the Mouse and the computer hardware can take one of three forms.

The Mouse Driver file

When DOS was first created the Mouse device did not exist and so no DOS support for this device was built into the DOS Operating System, or into the computers BIOS. This means a Mouse Driver file must be installed when the computer is booted and this add's the Mouse support to the operating system.

Devices like the Mouse can be supported at the DOS level by a file loaded from either the CONFIG.SYS or AUTOEXEC.BAT file. In the early days of DOS, Mice devices were supplied with both a .SYS and a .COM file, but only one of them was used. A .SYS file needed to be loaded from the CONFIG.SYS file with a line that read DEVICE = MOUSE.SYS (or whatever other name the .SYS file may have).

A .COM file is loaded from the AUTOEXEC.BAT file, and this is done by simply including the line mouse (or whatever other name the .COM file may have) in the AUTOEXEC.BAT file. Today Mouse support at a DOS level is only provided by a .COM file, and Windows 3.11 and later Operating System have Mouse support built in and do not need a Mouse support file.

Important: If you run a DOS session under Windows95 or later Operating System, you will usually need to load a Mouse Driver from the AUTOEXEC.DOS file. The AUTOEXEC.DOS file is used by Windows95 and above to provide support for heritage devices when going back to DOS.

There are quite a few brand of Mice available but most of them are compatible with one, or both, of the first two Mice available for the PC computer.

The Microsoft Mouse was the first one available and it was a two button mouse. A company called Mouse Systems then produced a three button mouse.

Originally each of these Mice required their own particular Mouse driver files but as other companies made Mice compatible with either of these original Mice, the Mice driver files got much smarter and could usually be made to emulate either type of Mouse. Some Mice have a switch on the bottom of the device that configures the Mouse as either a two button (Microsoft Mouse) or as a three button (Mouse Systems) Mouse. During the evolution of the Mouse at least one brand had a means of software switching (at boot up) between being a two button or a three button Mouse. It's Mouse driver file would only work with that brand of Mouse. Problems with older Mice and Mouse driver files are not uncommon, not all so called compatible Mice will work with Mouse driver files from other brands of Mouse.

The BIOS in many modern System Boards finds the Mouse connected to one of the Serial ports, or a PS/2 Interface, and uses it with the CMOS Setup screens. This facility does not supply DOS Mouse support, it only allows the Mouse to be used with the CMOS setup routines.

An alternative to the Mouse is the Track Ball but this is really only a Mouse turned on it's back and the user rotates the ball directly, rather than moving it over a flat surface. Another device that has been around for some years but has seen little use is the Pen Mouse. Many Lap-Top computers come with a tiny built in Mouse device that looks a bit like a very small joystick.

Mouse Maintenance

Mechanical Mice require regular cleaning as they suffer from dirt build-up on the ball and the rollers. This problem can be reduced by using a clean Mouse Mat in a clean work environment. When cleaning a mechanical Mouse you must remove the ball from the Mouse (or Track Ball), clean the ball with a lint free tissue and alcohol, and clean the three rollers inside the device with cotton buds and alcohol. The Honeywell Mouse does not suffer from the problem of dirt as much as the conventional Mice with a ball, or a Track Ball, and Optical Mice should need no maintenance at all.

The Digitizer Pad

An alternative pointing device used by most serious CAD users is the A Digitizer Pad. These devices are usually connected via a Serial port.

Important: A Joystick is not a Mouse device. A Joystick is connected to the Games Port and it generates analog signals (variable frequency signals) proportional to the X and Y position of the stick, wheel or pedal. A Mouse device generates pulses in response to movement of a ball or similar device.

Typical older Microsoft Bus Mouse The Microsoft Ergonomic Mouse Honeywell Mechanical Mouse A Digitizer Pad

The Track Ball A collection of mouse-like pointing devices Back to the opening index Book three index