INPUT AND OUTPUT DEVICES

INPUT DEVICES are devices we use to put information into a computer.

KEYBOARD

Keyboard Basics A keyboard's primary function is to act as an input device. Using a keyboard, we 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, numeric keypad, function keys, and control keys.

In 1986, IBM further extended the basic keyboard with the addition of function and control keys. Applications and operating systems can assign specific commands to the function keys. Control keys provide cursor and screen control. Four arrow keys arranged in an inverted T formation between the typing keys and numeric keypad move the cursor on the screen in small increments. Other common control keys include Home, End, Insert, Delete, Page Up, Page Down, Control (Ctrl), Alternate (Alt), Escape (Esc) The Windows keyboard adds some extra control keys: two Windows or Start keys, and an Application key.

The microprocessor and controller circuitry of a keyboard.

The key matrix

This keyboard uses rubber dome switches. Keyboard Switches This keyboard uses rubber dome switches.

Non-Traditional Keyboard Blue backlit keyboard 'on' Blue backlit keyboard 'off' Illuminated keyboards, like the Ion Illuminated Keyboard, use light-emitting diodes or electroluminescent film to send light through the keys or the spaces between keys.

From the Keyboard to the Computer As you type, the processor in the keyboard analyzes the key matrix and determines what characters to send to the computer. It maintains these characters in its memory buffer and then sends the data. A PS/2 type keyboard connector.

Microsoft wireless keyboard

SCANNER

The basic principle of a scanner is to analyze an image and process it in some way. Image and text capture (optical character recognition or OCR) allow you to save information to a file on your computer. You can then alter or enhance the image, print it out or use it on your Web page. Flatbed scanners, also called desktop scanners, are the most versatile and commonly used scanners. A typical flatbed scanner has Charge-coupled device (CCD) array, Mirrors, Scan head, Glass plate, Lamp, Lens, Cover, Filters, Stepper motor, Stabilizer bar, Belt, Power supply. Interface port (s), and Control circuitry.

Sheet-fed scanners are similar to flatbed scanners except the document is moved and the scan head is immobile. A sheet-fed scanner looks a lot like a small portable printer. Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them instead of a motorized belt. This type of scanner typically does not provide good image quality. However, it can be useful for quickly capturing text. Drum scanners are used by the publishing industry to capture incredibly detailed images.

The core component of the scanner Close-up of the CCD array

The Scanning Process the fluorescent lamp on top of the scan head. The document is placed on the glass plate and the cover is closed.

The image of the document is reflected by an angled mirror to another mirror. In some scanners, there are only two mirrors while others use a three mirror approach. Each mirror is slightly curved to focus the image it reflects onto a smaller surface. The last mirror reflects the image onto a lens. The lens focuses the image through a filter on the CCD array.

The filter and lens arrangement vary based on the scanner The filter and lens arrangement vary based on the scanner. Some scanners use a three pass scanning method. Each pass uses a different color filter (red, green or blue) between the lens and CCD array. After the three passes are completed, the scanner software assembles the three filtered images into a single full-color image.

Image Transfer Parallel - Connecting through the parallel port is the slowest transfer method available. Small Computer System Interface (SCSI) - SCSI requires a special SCSI connection. Most SCSI scanners include a dedicated SCSI card to insert into your computer and connect the scanner to, but you can use a standard SCSI controller instead. Universal Serial Bus (USB) - USB scanners combine good speed, ease of use and affordability in a single package. FireWire - Usually found on higher-end scanners, FireWire connections are faster than USB and SCSI. FireWire is ideal for scanning high-resolution images.

OUTPUT DEVICES are devices we use to get information out of a computer.

MONITOR A monitor is the screen on which words, numbers, and graphics can be seen. It is the most common output device.

LCDs vs. CRTs

Advantages of LCD Monitors Require less power Smaller and weigh less More adjustable Less eye strain

Advantages of CRT Monitors Less expensive Better color representation More responsive Multiple resolutions More rugged

Dual Monitors One way to expand your computer's display is to add a second monitor. Using dual monitors can make you more productive and add a lot to your computing experience.

With two monitors, you can: View large spreadsheets Make changes to a web page's code on one monitor and view the results on the second Open two different applications, such as a Word document on one monitor and your web browser on the second

Headset Canalphones (also known as in-ear monitors, or IEMs) are earphones that are inserted directly into the ear canal. Canalphones offer portability similar to ear buds, and also act as earplugs to block out environmental noise.

Webcam A webcam is a video capture device connected to a computer or computer network, often using a USB port or, if connected to a network, Ethernet or Wi-Fi.