Image scanners and optical character Recognition (OCR)

The bar code reader is a special type of image scanner. Image scanners also called scanners that convert any printed image into electronic form by shining light onto the image and sensing the intensity of the light's reflection at every point.
                  Color scanners use filters to separate the components of color into the primary additive colors at each point. Red , green and blue are known as primary additive colors because they can be combined to create any other color. Processes that describe color in this manner are said to use RGB color.
                 The image scanner is useful because it translates printed images into an electronic format that can be stored in a computer's memory. You can then use software to organize or manipulate the electronic image.
For example if you scan a photo , you can use adobe photo shop a graphic program to increase the contrast or adjust the colors. If you have scanned a text document , you might want to use optical character recognition (OCR) software to translate the image into text that you can edit. When a scanner first creates an image from a page, the image is stored in the computer's memory as a bitmap. A bitmap is a grid of dots, each dot represented by  one or more bits. The job of OCR software is to translate that array of dots into text that the computer can interpret as letters and numbers.
               To translate bitmaps into text, the OCR software loos at each character and tries to match the character with its own assumptions about how the letters should look. Because it is difficult to make a computer recognize an unlimited number of typefaces and fonts, OCR software is extremely complex.
             Despite the complexity of the task, OCR software has become quite advanced. Today , Many programs can decipher a page of text received by  a fax machine. In fact , computers with fax moderns can use OCR software to convert faxes directly into text that can be edited with a word processor. Scanners come in a range of sit on a desktop. Hand held scanners are more portable passes over a single  page because they are not as wide as letter - size paper. Flatbed  scanner offer higher quality reproduction than do handheld scanners and can scan a page in a single pass. Scans are sometimes required . To use  a flatbed scanner, you place  the printed image on a piece of glass similar to the way a page is placed on a photocopier . There are also medium  sized  scanners that are sheet fed ; that feed the sheet through the scanner, similar to the way a page is fed through a fax machine.

Optical Input Devices

For a long time, futurists and computer scientists have had the goal of enabling computers to "see". Computers may never see in the same way that humans do, but new technologies allow computers to use light as a source of input. these tools fall into the category of optical input devices.

Bar Code Readers:

The most widely used input device after the keyboard and mouse is a bar code reader. The most common type of bar code reader is the flatbed  model, which is commonly found in supermarkets and department stores. Workers for delivery services, such as Federal express, also use handheld bar code readers to identify packages in the field.
                           These devices convert a bar code , which is a pattern of printed bars on products , into a code the computer can understand. The bar code reader emits  a beam of light - frequently a laser beam - that is reflected by the bar code image. A light - sensitive detector identifies the bar code image by recognizing special bars at both ends of the image.  These special bars are different , so the reader can tell whether the bar code has been read   right side up or upside down.

After the detector has identified the bar code, it converts the individual bar patterns into numeric digits. the code reader then feeds that number to the computer, as though the number had been typed on a keyboard.

Devices for the Hand

Most input devices are designed to be used by hand. Even specialized devices like touch screens enable the user to interact  with the system by using his or her fingertips. Unlike keyboards and mice, many of these input devices are highly intuitive and easy to use without special skills or training.

Pens:

Pen based systems including many personal digital assistants and other types of handheld computers use a "pen" for data input. This pen like device is sometimes called a stylus. You hold the pen in your hand and write on a special pad or directly on the screen. You can also use the pen as a pointing device, like a mouse, to select commands.
              One might think that pen based systems would be a handy way to enter text into the computer for word processing. In reality , developers have had a great deal of trouble perfecting the technology so that it deciphers people's handwriting with 100 percent reliability. Because handwriting recognition is so complex, pen-based computers are not generally used to enter large amounts of text, although they are frequently used for note - taking and creating short messages.
             Pen-based computers are more commonly used for data collection, where the touch of a pen might select a yes or no box or mark a box next to a part that must be ordered or a service that has been requested . Another common use is inputting signatures or messages that are stored and transmitted as a graphic image, such as a fax. When delivery service drivers make deliveries , they often have recipients sigh their names on such  a computer based pad. As handwriting recognition technology becomes more reliable, pen-based systems will undoubtedly become more common.

Touch screen:

Touch screens accept input by allowing the user to place a fingertip directly on the computer screen, usually to make a selection from a menu of choices. Most touch screen computers use sensors in or near the computer's screen to detect the touch of a finger. Touch screens are appropriate  in environments where dirt  or weather would render keyboards and pointing devices useless, and where a simple, intuitive interface is important. They are well suited for simple applications such as automated teller machines or public information kiosks. Touch screens have become common in fast food restaurants, department stores, drug stores, and supermarkets, where they are used for all kinds of purposes, from  creating personalized greetng cards to selling lottery tickets. Car-rental agencies frequently provide touch screen systems at their counters so that customers systems at their  counters so that customers can quickly access and print out driving directions. Computerized touch screens also appear on slot machines in gambling casinos. Some computer makers refer to pen based systems as touch screen systems because the user touches the screen with a pen. However, the term touch screen implies a system that accepts input by allowing the user to touch the screen with a fingertip.

Game controllers:

You may not think of a game controller as an input device, but it is  personal computers are widely  used as gaming platforms, challenging long time video game units like the sony play station and others. Because PCs offer higher graphics resolution than  standard televisions, many games believe a well equipped PC provides a better game playing experience. If your computer is connected to the internet , you can also play games with people around the world.
         A game controller can be considered an input device because a computer game is a program, much like  a word processor. It accepts input from the user, processes data, and produces output in the form of graphics  and sound. As computer games become more detailed and elaborate, more specialized game controllers are being developed to take advantage of their features.
        Game controllers generally fall into two broad categories. game pads and joysticks. Joysticks have been around  for a long time and can be used with applications other than games. Joysticks enable the user to "fly" or "drive" through a game, directing a vehicle or character. They are popular in racing and flying games. A variant of the joystick is the racing game controller, which includes an actual steering wheel.

Alternative Methods of Input

Although the keyboard and mouse are the input devices that people use most often, several additional ways of getting data into a computer are available. Sometimes the tool is simply a matter of choice. Some users just prefer the feel of a trackball over a mouse. In many cases , however, an ordinary input device may not be appropriate. For example , in a dusty factory or warehouse, a keyboard or mouse can become clogged with dirt quickly. It takes time for grocery cashiers to input product codes and prices manually, so optical scanning devices are often used to speed the process and reduce the risk of input errors.

          Alternative input devices are important parts of some special purpose computers. Tapping an H/PC's screen with an electronic pen is much faster way to input commands than typing on a miniature keyboard. On the other hand, a specialized device can give new purpose to a standard system. If you want to play action packed games on your home  PC, for example, you will have more fun if you use a joy stick or game controller than a standard keyboard or mouse.

           This lesson examines several categories of alternative input devices and discusses the special uses of each. you may be surprised at how often you see these devices, and you may decide that an alternative device will be your primary means of interacting with your computer. 

        

Variants of the Mouse

As handy as it is, some people do not like using a mouse or have difficulty maneuvering one. For some, a mouse requires too much desktop space - a real problem when you do not always work at a desk!
             For these reasons and others, hardware makers have developed various input devices that duplicate the mouse's functionality but interact with the user in different ways. The Primary goals of these " mouse variants" are to provide ease of use while taking up less space than a mouse. They all remain stationary and can even be built into the keyboard.

The Trackball:

A trackball is a pointing device that works like an upside down mouse. You rest your thumb on the exposed ball and your fingers on the buttons. To move the pointer around the screen. You roll the ball with your thumb. Because  you do not move the whole device, a track ball requires less space than a mouse. When space is limited, a trackball can be an advantage. Trackballs gained popularity with the advent of laptop computers , which typically are used on laps or on small work surfaces without room for a mouse.

                   Like mice, trackball come in different models. Some trackballs are large and heavy , with a ball about the same size as a cue ball. Others  are much smaller. On portable computers, trackballs may be built directly into the keyboard, slide out of the system unit in a small drawer, or clamp to the side of the keyboard . Most trackballs feature two buttons, although three-button models are also available. Trackball units also are available in right and left handed models.

                  Some trackballs are not even attached to the computer and act like a remote control for the pointer . They are especially useful when giving presentations because  the presenter often walks  around the room instead of sitting at a computer.

The Track pad:

Track pad is a stationary pointing device that many people find less tiring to use than a mouse or track ball. The movement of a finger across a small touch surface is translated into pointer movement on the computer screen. the touch sensitive surface may be only 1.5 or 2 inches square, so the finger never has to move far. The track pad's size also makes it suitable for a notebook computer. Some notebook models feature a built in track pad rather than a mouse or trackball.

               Like mice, track pads usually are separate from the keyboard  in desktop computers and attach to the computer through a cord. some special keyboards feature built in track pads. this feature keeps the pad handy and frees a port that would otherwise be used by the track pad.

               Track pads include two or three buttons that perform the same functions as mouse buttons. some track pads are also " strike sensitive ". Meaning you can tap the pad with your fingertip instead of using the buttons.

                One draw back of track pads is that they must be kept clean and static free. Buildup of dust and oils from the user's fingers can affect a track pad's performance, making it less sensitive the touch.an unwanted static charge can make a track pad behave erratically.

Pointers in keyboard:

Several computer manufacturer now offer another space saving pointing device, consisting of a small joystick positioned near the middle of the keyboard, typically between the G and H keys. The joystick is controlled with either forefinger. Because users do not have to take their hands off the keyboard to use this device, it can save a great deal of time and effort. Two buttons that perform the same function as mouse buttons are just beneath the space bar and are pressed with the thumb. Because it occupies so little space the device is built into many different laptop mdels. This type of pointing device is also available on some models of desktop computer keyboards. 

           Several generic terms have emerged for this device many manufacturers refer to it as an integrated  pointing device, while others call it a 3-D point stick. On the IBM Think Pad line of notebook computers, the pointing device  is called the track point.

Mouse button Configuration

If you are left - handed, you can configure the right mouse button as the primary button. This configuration lets you place the mouse to the left of the keyboard, control the mouse with your left hand  and use your left forefinger for most mouse actions.
                Although the primary mouse button is used for most mouse actions, an increasing  number of programs also use the right mouse button. Windows 95, 98, 2000 and NT  use the right mouse button extensively to open shortcut menus. Using the right mouse button is know as right clicking.

How to use Mouse

You use a mouse to point to a location on the screen. Push the mouse forward across your desk and the pointer moves up: push the mouse to the mouse to the left, and the pointer moves to the left. To point to an object or location on the screen, you simply use the mouse to place the pointer on top of the object or location.

           Everything you do with a mouse you accomplish by combining pointing with four other techniques: clicking something with the mouse means to move the pointer to the item on the screen and to press and release the mouse button once. Double - clicking an item means to point to it with the mouse pointer and then press and release the mouse button twice in rapid succession. Dragging an item means to position the mouse pointer over the item, press the mouse button and hold it down as you move the mouse. As you move the pointer , the item is " dragged" along with it . you can then drop the item in a new position on the screen. This technique is called drag- and - drop editing.

               With Macintosh computers, most mice have only one button . with IBM - compatible computers, most mice have two buttons, but clicking, double clicking and dragging are usually carried out with the left mouse button. Some mice can have three or more buttons. The button uses are determined by the computers operating system, application software and mouse control software.

                A fairly recent enhancement is the wheel mouse. A wheel mouse has a small wheel nestled among its buttons. You can use the wheel for various purposes, one of which is scrolling through long documents. The mouse usually sits  to the right of the keyboard and users maneuvers the mouse with the right hand, pressing the left button with right forefinger. For this reason, the left mouse button is sometimes called the primary mouse button.