User Interface Design and Ergonomics - National Open University of ...

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UNIT 3 INPUT AND OUTPUT MODELS Table of Contents 1.0 Introduction 2.0 Objectives 3.0 Main Content 3.1 Input Model 3.2 Output Model 4.0 Conclusion 5.0 Summary 6.0 Tutor Marked Assignment 7.0 Further Reading and Other Resources 1.0 INTRODUCTION This unit looks at mechanics of implementing user interfaces, by looking at Input and Output model in detail. Different kinds of both input and output events will also be examined in greater detail. 2.0 OBJECTIVES By the end this unit, you should be able to: Explain the Input model Explain the Output model 3.0 MAIN CONTENT 3.1 INPUT MODEL Virtually all GUI toolkits use event handling for input. Why? Recall, when you first learned to program, you probably wrote user interfaces that printed a prompt and then waited for the user to enter a response. After the user gave their answer, you produced another prompt and waited for another response. Command-line interfaces (e.g. the Unix shell) and menu-driven interfaces (e.g., Pine) have interfaces that behave this way. In this user interface style, the system has complete control over the dialogue – the order in which inputs and outputs will occur. Interactive graphical user interfaces can not be written this way – at least, not if they care about giving the user control and freedom. One of the biggest advantages of GUIs is that a user can click anywhere on the window, invoking any command that’s available at the moment, interacting with any view that’s visible. In a GUI, the balance of power in the dialogue swings strongly over to the user’s side. 132
As a result, GUI programs can not be written in a synchronous, prompt-response style. A component can’t simply take over the entire input channel to wait for the user to interact with it, because the user’s next input may be directed to some other component on the screen instead. So GUI programs are designed to handle input asynchronously, receiving it as events. 3.1.1 KINDS OF INPUT EVENTS There are two major categories of input events: raw and translated. A raw event comes right from the device driver. Mouse movements, mouse button down and up, and keyboard key down and up are the raw events seen in almost every capable GUI system. A toolkit that does not provide separate events for down and up is poorly designed, and makes it difficult or impossible to implement input effects like drag-anddrop or video game controls. For many GUI components, the raw events are too lowlevel, and must be translated into higher-level events. For example, a mouse button press and release is translated into a mouse click event (assuming the mouse didn’t move much between press and release – if it did, these events would be translated into a drag rather than a click). Key down and up events are translated into character typed events, which take modifiers into account to produce an ASCII character rather than a keyboard key. If you hold a key down, multiple character typed events may be generated by an autorepeat mechanism. Mouse movements and clicks also translate into keyboard focus changes. When a mouse movement causes the mouse to enter or leave a component’s bounding box, entry and exit events are generated, so that the component can give feedback – e.g., visually highlighting a button, or changing the mouse cursor to a text Ibar or a pointing finger. 3.1.2 PROPERTIES OF AN INPUT EVENT Input events have some or all of these properties. On most systems, all events include the modifier key state, since some mouse gestures are modified by Shift, Control, and Alt. Some systems include the mouse position and button state on all events; some put it only on mouse-related events. The timestamp indicates when the input was received, so that the system can time features like autorepeat and double-clicking. It is essential that the timestamp be a property of the event, rather than just read from the clock when the event is handled. Events are stored in a queue, and an event may languish in the queue for an uncertain interval until the application actually handles it. User input tends to be bursty – many seconds may go by while the user is thinking, followed by a flurry of events. The event queue provides a buffer between the user and the application, so that the application doesn’t have to keep up with each event in a burst. 133
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] NATIONAL OPEN UNIVERSITY OF NIGER
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National Open University of Nigeria
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Summary ...........................
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UNIT 3 - GRAPHICAL USER INTERFACE (
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Assignments File Tutor-Marked Assig
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2 DESIGN and DESIGNING GOOD USER IN
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need both the study unit you are wo
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CIT 711: USER INTERFACE DESIGN AND
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UNIT 1 FUNDAMENTALS OF USER INTERFA
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3.3 TYPES OF USER INTERFACES Curren
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3.5 USER INTERFACE MODALITIES AND M
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Table of Contents 1.0 Introduction
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3.1.1 DESIGNING A GOOD USER INTERFA
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widgets properly is to read and und
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Figure 1:- Showing that alignment o
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6.0 TUTOR MARKED ASSIGNMENT a. How
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A graphical user interface is a typ
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Operating System. It is easy for a
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A list of items from which to selec
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collaborative work. For example, sc
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MODULE 1 UNIT 4 HUMAN COMPUTER INTE
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3.3 DIFFERNCES WITH RELATED FIELDS
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window blinds to automobile braking
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Wickens, Christopher D., John D. Le
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The International Ergonomics Associ
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approach, the Gilbreths reduced the
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3.6 BENEFITS OF ERGONOMICS The thre
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Another key to reducing lumbar disc
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MODULE 2 - USER INTERFACE DESIGN TE
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methods include inspection methods,
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Determine time of each operation (b
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unable to understand new informatio
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M cones, or, misleadingly, green co
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Motor skill which is a learned seri
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MODULE 2 UNIT 2 UNDERSTANDING USERS
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The users of a system must be ident
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This example brings up an important
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whether you want to have a palette
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Task analysis which includes identi
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MODULE 2 UNIT 3 USER CENTERED DESIG
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Page 84 and 85: Introduction to User-centered desig
Page 86 and 87: organizations themselves. Interacti
Page 88 and 89: After thorough analysis using vario
Page 90 and 91: Interaction design which is the dis
Page 92 and 93: In human-computer interaction and c
Page 94 and 95: The preferred method for ensuring u
Page 96 and 97: 3.4 ISO STANDARDS FOR USABILITY ISO
Page 98 and 99: In this unit, you have been introdu
Page 100 and 101: affect the way the command is execu
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Page 104 and 105: The term direct manipulation was in
Page 106 and 107: There are two important reasons for
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Page 110 and 111: UNIT 1 PROTOTYPING Table of Content
Page 112 and 113: Figure 12: The iterative steps of p
Page 114 and 115: select print Figure 13: An interfac
Page 116 and 117: Ambler, S.W. & Constantine, L.L. (2
Page 118 and 119: 3.2 LOW-FIDELITY PROTOTYPES Low-fid
Page 120 and 121: Figure 14:- Example of Sketching II
Page 122 and 123: Much more important for features th
Page 124 and 125: DENIM, an extension of SILK, is a t
Page 126 and 127: • Encourage menu & forms style, r
Page 128 and 129: Another problem is that native widg
Page 130 and 131: interfaces, so that a realistic sim
Page 134 and 135: Recall that perceptual fusion means
Page 136 and 137: 3.2 OUTPUT MODEL There are basicall
Page 138 and 139: directly-mapped pixel image will no
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Page 142 and 143: UNIT 4 MODEL VIEW-CONTROLLER (MVC)
Page 144 and 145: 3.3.2 AS A DESIGN PATTERN MVC enco
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Page 148 and 149: UNIT 5 LAYOUTS AND CONSTRAINTS Tabl
Page 150 and 151: 3.5 CONSTRAINTS Constraints are rel
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Page 154 and 155: MODULE 4 UNIT 1 TECHNIQUES FOR EVAL
Page 156 and 157: a. Card Sorting Card sorting is a w
Page 158 and 159: Rapid prototyping is a method used
Page 160 and 161: 3.2.1 THE USE OF PROTOTYPES It is o
Page 162 and 163: Dumas, J.S. and Redish, J.C. (1999)
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Page 170 and 171: Table 4:- Table: Average times for
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Page 176 and 177: 7.0 REFERENCES AND FURTHER READING
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It's very easy to shape the comment
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a. Analyzing the Bottom-Line Number
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you use. But then you need some way
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ecruit test users with more similar
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MODULE 4 UNIT 4 OTHER EVALUATION IS
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3.2 CURRENT ISSUES CONCERNING EVALU
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2.0 OBJECTIVES By the end this unit
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It provides a real focal point for
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3.3.4 CONDUCTING THE TEST Having co
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The stages involved in usability te
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