[ Team LiB ] Previous Section Next Section


To communicate its codes to your computer, any pointing device needs to be connected in some way. Notebook computers have it easy—signals can take the direct route because they are built in. Desktop systems require some kind of port to which you can connect your mouse or other pointing device. Most systems today have a dedicated mouse port. But the industry-wide push to eliminate legacy ports of any kind, as well as the need for alternative pointing devices, are making the USB interface popular (at least among computer-makers). A few mice using the legacy RS-232C serial port are also available.

Mouse Port

The most popular way to connect a mouse to a desktop computer is via the mouse port. Physically the mouse port resembles a keyboard jack. Both use a six-pin miniature DIN connector. The design owes its heritage to the first IBM Personal Systems/2 (PS/2) and consequently is sometimes termed a PS/2 mouse port. The only lasting change affected by the computer industry on this port design has been color-coding. To distinguish a mouse port from a keyboard port, the mouse port jack and connector are colored aqua, a bluish green. (Keyboard ports are purple.)

Electrically the mouse port is also similar to a keyboard port, using low-speed serial technology to send signals from mouse to computer using its own interrupt to avoid conflicts with other devices. This design limits the use of the mouse port because it is not fast enough to handle the needs of more sophisticated pointing devices.

USB Port

True to the "universal" in its name, the USB port accommodates mice and any other kind of pointing device. The port, even in its early Version 1.0 form, offers enough speed for the most elaborate pointing devices. Moreover, because pointing devices are not used during bootup before the operating system and its drivers load, there's no need for special BIOS provisions for handling USB mouse control. The hardware installation of a USB-based pointing device requires only plugging it in, which is why this connection system is preferred.

Serial Mice

The serial port was the first connection system used by mice, and its shortcomings provided the incentive to develop the dedicated mouse port. In general, mice make no onerous demands on the serial port. They operate at a low communication rate (1200 bits per second) and adapt to any available port thanks to driver software. But putting a mouse on a serial port is hardly trouble-free. Because every mouse movement generates a serial-port interrupt, if your system has more than two serial ports, you can easily generate interrupt conflicts with a mouse. Because serial ports 1 and 4 (that is, the ports that DOS calls COM1 and COM4) share interrupt 4, and serial ports 2 and 3 (COM2 and COM3) share interrupt 3, a mouse can conflict with another device connected to the other port sharing its interrupt. If you have a serial mouse, it's always best to plug your mouse into the port that does not have to share its interrupt (for example, COM1 if your computer has three serial ports) to avoid surprises—the kind that can crash your computer. Better still, use a mouse port or USB mouse.


The most irksome trait of the mouse is the tail that inspired its name. The cord dangling from the far end of the mouse is a desktop hazard, liable to snag whatever you're working on. Thank goodness that inkwells are about as likely as chimera on modern desks; otherwise, you could count on your mouse making your work a uniform ink-stained blue at least once a day. Mice consequently benefit from wireless technology even more than keyboards.

Making a mouse wireless is much the same as cutting the keyboard cord. The wireless link operates between the mouse and a base station, which connects to your computer through one of the aforementioned standard mouse interfaces. The wireless link is proprietary, allowing the manufacturer to chose whatever technology and design best fits the purpose and price of the product.

Infrared (IR) technology, although chosen by some manufacturers, does not mate with the typical cluttered desktop environment. The IR sensor in the base station must be able to see the mouse—literally—and any object in the way can create errors of omission, undetected mouse movements. If you confine your mouse to a pad, you can put the base station adjacent to the pad without risk of losing communication. But with today's optical mouse technologies, the temptation is to move your mouse on any suitable desktop bare spot, which may not be near the base station.

Radio technology is a better match for the lifestyle of the modern mouse, and most manufacturers have shifted to it. Because radio waves penetrate most desktop objects, you can put the base station almost anywhere and still expect your mouse to work.

If you're thinking of going wireless, a better choice is to buy a wireless keyboard and mouse as a package so you need only one base station for both.

    [ Team LiB ] Previous Section Next Section