INPUT

In this chapter, you learn what input is and what input devices are. The keyboard is presented and different keyboard types are described. You are introduced to various pointing devices, such as the mouse, trackball, touchpad, pointing stick, joystick, touch screen, and pen input. Scanners and reading devices, including optical scanners, optical readers, magnetic ink character recognition readers, and data collection devices are explained. You learn about digital cameras, audio input, speech recognition, video input, and videoconferencing. Finally, input devices for physically challenged users are explored.

Describe the two types of input

Input is any data or instructions entered into the memory of a computer. Two types of input are data and instructions.

Data is a collection of unorganized items that can include words, numbers, pictures, sounds, and video. A computer processes data into information, which is organized, meaningful, and useful.

Instructions can be in the form of programs, commands, or user responses.

A program is a series of instructions that tells a computer how to perform the tasks necessary to process data into information.

A command is an instruction given to a computer program.

A user response is an instruction you issue to the computer by responding to a question posed by a computer program.

Any hardware component that allows you to enter data, programs, commands, and user responses into a computer is an input device.

List the characteristics of a keyboard

The keyboard is an input device that contains keys you press to enter data into a computer. Desktop computer keyboards usually have from 101 to 105 keys, while keyboards for smaller computers contain fewer keys.

All keyboards have a typing area used to type letters of the alphabet, numbers, punctuation marks, and other basic characters.

Many desktop computer keyboards also have

·         a numeric keypad designed to make it easier to enter numbers,

·         function keys programmed to issue commands and accomplish certain tasks,

·         arrow keys used to move the insertion point (a symbol on the screen that indicates where the next typed character will display), and

·         Toggle keys that can be switched between two different states.

Identify various types of keyboards

A standard computer keyboard sometimes is called a QWERTY keyboard because of the layout of its typing area.

An enhanced keyboard has 12 function keys along the top row, 2 ctrl keys, 2 alt keys, and a set of arrow and additional keys between the typing area and the numeric keypad.

Cordless keyboards transmit data via infrared light waves.

Keyboards for notebook and handheld computers usually have smaller and fewer keys than desktop computers.

A portable keyboard is a full-sized keyboard you can attach to and remove from a handheld computer.

Some manufacturers have designed ergonomic keyboards to reduce the chance of workplace injuries. The goal of ergonomics is to incorporate comfort, efficiency, and safety into the design of workplace items.

Identify various types of pointing devices

In a graphical user interface, the pointer is a small symbol on the screen. A pointing device is an input device that allows you to control the pointer. Common pointing devices include the mouse, trackball, touchpad, pointing stick, joystick, touch screen, light pen, and a stylus.

·         A mouse is a pointing device, designed to fit comfortably under the palm of your hand, that is moved across a flat surface.

·         A trackball is a stationary pointing device with a ball mechanism on its top.

·         A touchpad is a flat, rectangular pointing device that is sensitive to pressure and motion.

·         A pointing-stick is a pressure-sensitive pointing device shaped like a pencil eraser that is positioned between keys on the keyboard.

·         A joystick is a vertical lever mounted on a base.

·         A light pen is a handheld device that contains a light source or can detect light.

·         A touch screen is a touch-sensitive display on the screen.

·         A stylus looks like a ballpoint pen but uses pressure, instead of ink, to write text and draw lines.

·         An electronic pen can be used on a graphics tablet, which consists of a flat, rectangular, electronic plastic board used to input graphical data.

Explain how a mouse works

As you move a mouse across a flat surface, the movement is translated into signals that are sent to the computer, and the pointer on the screen also moves. When you move the mouse to the right, the pointer moves to the right on the screen. For Windows users, the top of a mouse has at least two buttons and sometimes also a wheel. Generally, you use a mouse to move the pointer on the screen to an object and then press a button, or click, to perform a certain action on that object. Other operations you can perform using a mouse include right-click, double-click, drag, right-drag, rotate wheel, and press wheel button.

Describe different mouse types

A mechanical mouse has a rubber or metal ball on its underside. When the ball rolls in a certain direction, electronic circuits in the mouse translate the movement into signals that are sent to the computer. For better traction, you should place a mechanical mouse on a mouse pad.

An optical mouse has no moving parts; instead it uses devices that emit and sense light to detect the mouse’s movement. An optical mouse can be used on nearly all surfaces, is more precise than a mechanical mouse, and does not require cleaning.

A cordless mouse, or wireless mouse, is a battery powered device that transmits data using wireless technology, such as radio waves or infrared light waves. A cordless mouse uses technology very similar to that of a cordless keyboard.

Explain how voice recognition works

Voice input is the process of entering data by speaking into a microphone that is attached to the sound card on a computer. Voice recognition is the computer’s capability of distinguishing spoken words. The first voice recognition programs were speaker dependent. With speaker-dependent software, the computer makes a profile of your voice, which means you have to train the computer to recognize your voice. Today, most voice recognition programs use speaker-independent software, which has a built-in set of word patterns and does not have to be trained to recognize your voice. Some voice recognition software requires discrete speech, meaning that you have to speak slowly and separate each word with a short pause. Most voice recognition products, however, support continuous speech, allowing you to speak in a flowing conversational tone.

Understand how to input data into a handheld computer

To satisfy the input needs of many different types of users, handheld computers provide many different ways to input data. A handheld computer typically includes a basic stylus. With the stylus, you can enter data using an on-screen keyboard or using handwriting recognition software that translates handwritten letters and characters into symbols the computer understands. Other input alternatives available with some handheld computers include attaching a full-sized keyboard, transferring data from a desktop computer, using voice input, and attaching a digital camera.

Identify the uses of a digital camera

A digital camera is used to take pictures and store the photographed images digitally instead of on traditional film. Pictures are stored on a storage medium, such as a floppy disk, SuperDisk, Clik! disk, PC Card, compact flash card, memory stick, mini-CD, or microdrive. Many digital cameras allow you to review and edit the images while they are in the camera. You also can download, or transfer a copy of, the stored image to a computer. Once on a computer, the pictures can be edited with photo-editing software, printed, faxed, sent via electronic mail, included in another document, or posted to a Web site.

There are three basic types of digital cameras.

A studio camera is a stationary digital camera used for professional studio work.

A field camera is a portable camera, often used by photojournalists, that has many lenses and other attachments.

A point-and-shoot camera is more affordable and lightweight and provides acceptable quality photographic images for the home or small business user.

Describe the various techniques used for video input

Video input, or video capture, is the process of entering a full-motion recording into a computer and storing the video on a storage medium.

Many video devices use analogue video signals. To input video from these devices, the device is plugged into a video capture card, an expansion card that converts the analogue signal into a digital signal the computer can understand.

A digital video (DV) camera is a new generation of video camera that records video as digital signals, instead of using analogue signals, and therefore does not require a video capture card. Video files can demand huge amounts of storage space.

Video compression reduces the size of video files by recognizing that only a small portion of an image changes from frame to frame. Instead of storing every frame in its entirety, a video compression program might store an initial frame and then store only the changes from one frame to the next.

A video decoder is a card that decompresses video. A video digitizer can be used to capture an individual frame from a video and save the still picture in a file.

Describe the uses of PC video cameras and Web cams

A PC camera is a DV camera that allows home users to record, edit, capture video and still images, and make video telephone calls on the Internet. During a video telephone call, both parties can see each other as they talk. Although usually placed on top of the monitor and attached to a computer’s USB port, some PC cameras are portable and can be used anywhere.