Computer Mouse

The Mouse is the device you will use for most of your interactions with your PC. It is primarily used to move the pointer arrow around the screen and to select and activate options.

The mouse buttons are used to interact with whatever is on the screen where the pointer is located. The left mouse button is the one you will use most often. Clicking this tells the PC to select an item and is called 'left-clicking'. To activate an item and use it, you will often need to click the button twice or 'double-click'.

If you click and hold the left button and move the mouse, this has the effect of 'dragging' a selected object about the screen until you release the button.

Left-clicking on text in a document will place a flashing cursor at that point, which allows you to begin typing there.

The right mouse button is usually used to bring up a small menu window that gives options specific to the selected object. To use a particular option you just left-click it.
Common right-click menu options for an object include: Open (activate, same as if you double-click), Cut (remove to be placed elsewhere), Copy (make a copy of this object) , Create Shortcut (create a shortcut link elsewhere to give quick access to this object), Delete (remove permanently), Rename (give a new name), and Properties (find out information).

You may have a third smaller button in the center of your mouse that can be rolled forwards and backwards. This mouse-wheel can be used to move up and down through documents.

What are the bumps at the end of computer cables?

In a typical computer system found in a home or office, you normally see these "bumps" on the mouse, keyboard and monitor cables. You can also find them on power supply wires when a device (like a printer or scanner) uses an external transformer.

These "bumps" are called ferrite beads or sometimes ferrite chokes. Their goal in life is to reduce EMI (electromagnetic interference) and RFI (radio-frequency interference). You can see these beads in the photo on to your right.

A ferrite bead is simply a hollow bead or cylinder made of ferrite, which is a semi-magnetic substance made from iron oxide (rust) alloyed with other metals. It slips over the cable when the cable is made, or it can be snapped around the cable in two pieces after the cable is made. The bead is encased in plastic -- if you cut the plastic, all that you would find inside is a black metal cylinder.

Computers are fairly noisy devices. The motherboard inside the computer's case has an oscillator that is running at anywhere from 300 MHz to 1,000 MHz. The keyboard has its own processor and oscillator as well. The video card has its own oscillators to drive the monitor. All of these oscillators have the potential to broadcast radio signals at their given frequencies. Most of this interference can be eliminated by the cases around the motherboard and keyboard.

Another source of noise is the cables connecting the devices. These cables act as nice, long antennae for the signals they carry. They broadcast the signals quite efficiently. The signals they broadcast can interfere with radios and TVs. The cables can also receive signals and transmit them into the case, where they cause problems. A ferrite bead has the property of eliminating the broadcast signals. Essentially, it "chokes" the RFI transmission at that point on the cable -- this is why you find the beads at the ends of the cables. Instead of traveling down the cable and transmitting, the RFI signals turn into heat in the bead.

How do optical mice work?

It appears that the venerable wheeled mouse is in danger of extinction. The now-preferred device for pointing and clicking is the optical mouse.

Developed by Agilent Technologies and introduced to the world in late 1999, the optical mouse actually uses a tiny camera to take 1,500 pictures every second. Able to work on almost any surface, the mouse has a small, red light-emitting diode (LED) that bounces light off that surface onto a complimentary metal-oxide semiconductor (CMOS) sensor. The CMOS sensor sends each image to a digital signal processor (DSP) for analysis. The DSP, operating at 18 MIPS (million instructions per second), is able to detect patterns in the images and see how those 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 wheeled 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 smoother response.
· They don't require a special surface, such as a mouse pad.

In the photo on top, you can see the LED on the bottom of the mouse.

Keyboard Basics

When you look at all the extras and options that are available for new computer keyboards, it can be hard to believe that their original design came from mechanical typewriters that didn't even use electricity. Now, you can buy ergonomic keyboards that bear little resemblance to flat, rectangular models with ordinary square keys. Some flashier models light up, roll up or fold up, and others offer options for programming your own commands and shortcuts. They use switches and circuits to translate a person's keystrokes into a signal a computer can understand.

A keyboard's primary function is to act as an input device. Using a keyboard, a person can type a document, use keystroke shortcuts, access menus, play games and perform a variety of other tasks. Keyboards can have different keys depending on the manufacturer, the operating system they're designed for, and whether they are attached to a desktop computer or part of a laptop. But for the most part, these keys, also called keycaps, are the same size and shape from keyboard to keyboard. They're also placed at a similar distance from one another in a similar pattern, no matter what language or alphabet the keys represent.

Most keyboards have between 80 and 110 keys, including:

- Typing keys
- A numeric keypad
- Function keys
- Control keys

The typing keys include the letters of the alphabet, generally laid out in the same pattern used for typewriters. According to legend, this layout, known as QWERTY for its first six letters, helped keep mechanical typewriters' metal arms from colliding and jamming as people typed. Some people question this story – whether it’s true or not, the QWERTY pattern had long been a standard by the time computer keyboards came around. typing keys include the letters of the alphabet, generally laid out in the same pattern used for typewriters. This layout, known as QWERTY for its first six letters, helped keep mechanical typewriters' metal arms from colliding and jamming as people typed. Because this pattern had been long established as a standard, manufacturers developed keyboards for computers using the same layout, even though jamming was no longer an issue.

What if I am out of USB ports in my PC?

Just about every peripheral made now comes in a USB version. Here's a list of some of the USB devices that you can buy today:

Printers, Scanners, Mice, Joysticks, Digital cameras, Webcams, Modems, Speakers, Telephones, Video phones, Storage devices like Zip drives, Network connections, etc.

Computers that you buy may come with only one or two USB sockets. With so many USB devices on the market today, you easily run out of USB sockets very quickly.

For example, on the computer that I am typing on right now, I have a USB printer, a USB scanner, a USB Webcam and a USB network connection. My computer has only one USB connector on it, so the obvious question is, "How do you hook up all the devices?"

The easy solution to the problem is to buy an inexpensive USB hub. The USB standard supports up to 127 devices.

A hub typically has four new ports, but may have many more. You plug the hub into your computer, and then plug your devices (or other hubs) into the hub. By chaining hubs together, you can build up dozens of available USB ports on a single computer.