Introduction

When people talk about input/output, it is often talked about in the abbreviated form I/O (pronounced "eye-oh"). Input refers to the equipment, device, or operation that enters data into the computer. Primary input examples are the keyboard and the mouse. Output is the way of getting data from the computer. This would be the monitors and printers.

Input Devices

First we will discuss ways to input data. There are numerous names for the different input devices. Some examples are: CCD, digital camera, digitizing tablet, grabber, graphics tablet, HMD, input device, IrDA, joystick, keyboard, light pen, mouse, optical reader, pointing device, pointing stick, puck, source, standard input, stylus, tablet, touch pad, track ball, and voice recognition. An input device gathers input and translates it into a form that the computer can process.

For the purpose of this tutorial, we will highlight the more common input devices, namely the keyboard and mouse.

Keyboards

The main input device for most computer systems is the keyboard. It enables you to type data and computer instructions into your computer system. Most standard keyboards have four basic components. A typing keypad (similar to the typewriter keys), function keys (F1 - F12), a numeric keypad (like a calculator keypad), and editing keys (cursor keys, home, end, etc.).

What happens when you press a key? Answer

Keyboards come within a variety of shapes, features, appearances, and costs. These are all things to keep in mind when deciding on what type of keyboard will best meet your needs.

Who is the fastest typist in the world? Answer

Mouse

Back when operating systems were developed in DOS, the keyboard was pretty well the only way that people could input information into computers. It was not until 1984 that the Apple Macintosh popularized the mouse.

The main advantage of a mouse over the keyboard is that it is simple to use. Some operations are so much easier to perform with a mouse than a keyboard. When you move the mouse on your desk, a pointer (usually an arrow) moves on the screen corresponding to how you move the mouse. The pointer will only move when the underside of the mouse (the ball part) is in contact with a hard surface like a desk. You can select an object on the screen by pressing the left mouse button a single time. You can also double click, drag and move objects on the screen.

Who invented the mouse? Answer

Ever wonder why some mice have a one, two or three buttons? The mouse used with a Macintosh computer only has one button. IBM-compatible computers use either a two- or three-button mouse. A two-button mouse, for example, allows you to click the left button and select an object. If you click the right button on that object, it might bring up a menu of actions that you can do with the object. On a three-button mouse you may be allowed to click the middle button once instead of double-clicking the left mouse button. This feature is useful for people who have trouble double-clicking.

Output Devices

Any machine capable of representing information from a computer is considered an output device. Their function is to display, print, or transfer the output, or results, of processing from the computer memory. This includes display screens, printers, plotters and synthesizers. The primary output devices we will focus on in this tutorial will be monitor screens and printers.

Monitors

Monitors convert electrical signals from the computer into points of coloured light on the screen to form an image. Most monitor screens work under the same principle as a television by using a cathode ray tube (CRT). The term CRT is often used in place of display screen.

The first type of monitors and display terminals were character-based. This type uses only one color (green, amber or white) to display text on a black background. The characters on the screen cannot be changed. In other words, you cannot display different sizes or styles of characters. The only graphics that you can have on character-based displays are those composed of underlines, exclamation points and other symbols that already exist in the character set.

Even though there appears to be "colour" on the screen of a character-based display, it is technically classified as a monochrome display.

The more modern and common type of display is the graphics or bit-map display. A graphics display or bit-map display divides the screen into a matrix of small dots called pixels. Any characters or graphics the computer displays on the screen must be constructed with dot patterns within the screen matrix.

The more dots your screen displays in the matrix, the higher the resolution. A high-resolution monitor can produce complex graphical images and text that is easier to read than on a low-resolution monitor.

Touch sensitive screens display options you can select by touching them on the screen.

Printers

Printers are devices that print text or illustrations on paper. There are many different types of printers. Two categories are impact and non-impact. Impact printers include all printers that work by striking an ink ribbon. Daisy-wheel, dot-matrix, and line printers are impact printers. Non-impact printers include laser printers and ink-jet printers.

The most common printers sold at this time are the dot-matrix, laser, and ink-jet. Dot-matrix printers are sold mostly to businesses for carbon-copy invoice printing. Laser and ink-jets tend to be more common for both business and personal use.

More specifically, here is the differences between how each of these printers operate. Dot-matrix printers create characters by striking pins against an ink ribbon. Each pin makes a dot, and combinations of dots form characters and illustrations. Ink-jet printers spray ink at a sheet of paper. Ink-jet printers produce high-quality text and graphics. Laser printers use the same technology as copy machines. Laser printers produce very high quality text and graphics.

Some important features of the different printers are speed, graphics capability, fonts, and color. Speed is measured in characters per second (cps) or pages per minute (ppm). The speed of printers varies widely. Dot-matrix printers can print up to 500 cps, and laser printers range from about 4 to 20 text pages per minute. All three of these printers are able to print both text and graphics. Dot-matrix printers are limited to one or a few fonts. In contrast, laser and ink-jet printers are capable of printing an almost unlimited variety of fonts.

Input Devices Information on Input Devices. http://webopedia.internet.com/Hardware/Input_Devices/

References