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Chapter 3Input Devices

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Overview of the Input Process

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The Input Process Input - the first stage of information

processing. Input devices that capture, collect, and

transmit data and programs, include:· sensors· keyboards· pointing devices· scanners

The primary purpose of any input device is to send the computer digital code that accurately represents some kind of real-world state or activity.

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Input Devices for Analog Activity

An analog sensor converts analog data into electronic signals of varying voltage. These signals are called analog signals.

An analog-to-digital converter transforms analog signals into a series of on-off electronic pulses.

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Real-Life Example

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Interactive Input Devices

An interactive input device is a hardware component that provides for human interaction as it captures, collects, and transmits data and programs to the computer in a form that the computer can understand.

Examples include:· keyboards· pointing devices· scanners

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The Keyboard

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A keyboard is an electronically controlled device used to enter alphanumeric data (letters, numbers, and special

characters) into the computer.

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Sensing a Keystroke

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Pointing Devices

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Pointing Devices

Pointing devices - offer alternatives to the keyboard. The graphics cursor is separate from the text cursor.

The graphics cursor may appear as a straight line (|), an arrow (<--), a cross-hair (+), or a variety of other symbols, depending on the software application you are using and where the graphics cursor is positioned.

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Mouse A mouse is hand-held pointing device whose

movement across a flat surface causes a corresponding movement of a graphics cursor on the screen.

Electromechanical mouse - contains a small ball at its base that rotates as it is moved.

Optical mouse - contains a light-source and sensor that, when moved along a surface of a special grid, relays movement information to the computer.

GUI (graphical user interface) - uses pictures, called icons, to represent actions such as opening, saving, or printing a file.

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Trackball

A trackball consists of a ball sitting on rollers, inset in a small external case or, in many notebook computers, in the same unit as the keyboard.

The main advantage of a trackball is that it requires less desk space than a mouse. The trackball also requires less arm movement than the mouse, making it a valuable resource for those with limited arm mobility.

Trackballs are often used in notebook computers.

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Other Pointing Devices

A touch screen can detect where a user “touches” the screen, thus enabling the user to issue a command or select an option by touching the appropriate spot.

A light pen detects light coming from the screen with a highly sensitive photoelectric cell, allowing the user to draw images, make selections, etc.

A digitizer tablet is a flat tablet imbedded with a grid of thousands of wires that make contact at a particular point when a stylus is passed over it.

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Other Interactive Input Devices

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Other Interactive Input Devices

Pen-based computers allow the user to enter data and/or commands by writing on the screen.

Point-of-sale terminals are smart terminals that allow the capture of sales, inventory and even customer data when the transaction occurs.

Financial transaction terminals are used to perform banking-related activities. The ATM (automated teller machine) is a particularly familiar form of the financial transaction terminal.

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Source Data Automation Devices

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Source Data Automation

Collecting data at its source and sending it directly to the computer without any keystrokes being required is called source data automation.

Because source data automation minimizes the need for human intervention in the input process, it increases accuracy, speed and reliability.

Although previously discussed input devices may be used for source data automation, they usually consist of some kind of scanning mechanism and a means for interpreting the scanned image.

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Source Data Automation Devices

The basic optical scanner converts photos, drawings, forms and/or text into digital form.

Optical character recognition (OCR) involves reading a set of pre-defined shapes, recognizing specific patterns in those shapes and interpreting them in the context of the application.

Optical marks, codes and characters are all examples of sets of shapes used to convey data in particular settings.

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Source Data Automation Devices (continued)

Magnetic ink character recognition (MICR) is used almost exclusively by the banking industry. In addition to being rather unique in shape, the characters are printed with magnetic ink.

A magnetic-strip card stores information in magnetic form on a small magnetic strip. Credit cards often contain magnetic strips.

A smart card is about the size of a credit card, but contains a built-in microcomputer and memory.

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Multimedia Input Devices

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Multimedia Input Devices

Audio input devices are used to receive, digitize and store audio signals, including the human voice. The digitized data may be simply stored for later replay or it may be input into a voice recognition system that converts recorded voice data into ASCII characters.

Video input devices receive and digitize video signals for later replay or input into a process control system, inspection system or other system that makes use of visual images.