User Interface Design. Interface Design 4. User Interface Design. User Interface Design. User Interface Design. User Interface Design

Transcription

1 Specification of a conversation between the user and the computer. Generally results in either input, output or both. An important part of systems and software development. An intuitive and easy to use interface leads to a more usable system. March 06 Interface Design 1 Display Terminals & Monitors Design of UI can be enhanced or restricted by the features available on terminals or keyboards Display Area Size of display area critical to UI design. Two most common display areas are 25*80 lines and 25*132. Some displays can be shuffled between these. March 06 Interface Design 2 Some terminals can show up to four screens simultaneously. In a PC display, area is measured in pixels. The greater the number of pixels, the larger the amount of information that can be displayed. Pixel areas are specified in width and height:- 640*480 or 1024*768 March 06 Interface Design 3 Character Sets & Graphics Every display uses a predefined character set:- ASCII set and UNICODE set. Some displays allow the programmer to supplement or replace the predefined character set. Graphics capabilities must be supported by graphics controllers (cards) and software to allow the programmer to take advantage of the March 06graphics. Interface Design 4 Character Sets & Graphics Graphic displays may support a virtually unlimited character set (UNICODE). Paging & Scrolling Manner in which the display area is shown to the user is controlled by:- technical capabilities of display software capabilities of the system Paging display complete area (page, screen or frame) of character at one time, replaced on demand Scrolling move displayed characters up or down one line at a time March 06 Interface Design 5 March 06 Interface Design 6

2 Colour & Display Properties Modern displays capable of colour. Highlight specific messages, data or areas of the screen. Variety of display properties supported:- double brightness on selected areas, blinking, nondisplay (passwords), reverse video (swap foreground and background), shadow March 06 Interface Design 7 Split Screens - a variation of the windows concept display screen can be divided into distinct areas (windows) under software control. Each window can:- act independently of others, using scrolling, display attributes and colour. be defined to serve a different purpose. March 06 Interface Design 8 Each window can:- be moved, resized, hidden or recalled on user demand Windows has become the de facto standard UI most OS provide Windows like GUI - Windows, Linux etc. Windowing Capabilities Common User Access (CUA) Set of rules (standard) that defines the way in which a system user interacts with a computer application. The goal is to provide the system user with a familiar computer interface across many different computer applications. March 06 Interface Design 9 March 06 Interface Design 10 CUA It includes rules governing use of a keyboard, mouse, selection of menu choices, accessing help, moving between applications. It provides for a standard look and feel which reduces training time and errors, increasing productivity. The most common implementation is the GUI GUI Uses icons (graphic symbols), pop up windows, scroll bars and pull down menus to communicate with the user. Its success due to ease of use and intuitiveness. A GUI can reduce input error and time taken to key in data by providing radio buttons, check boxes and drop down lists. March 06 Interface Design 11 March 06 Interface Design 12

3 Keyboard & Function Keys Function keys - usually labelled F1, F2. can be used to implement certain common, repetitive operations in a user interface. Help - F1, Refresh - F5, Page up, Page down These keys and combinations of others can be programmed to perform certain tasks:- ALT + PRNT SCRN - screen capture ALT + F open the file menu March 06 Interface Design 13 Human Factors Most important for user interface design. User can be either dedicated or casual (generally). Dedicated system user Will spend a considerable amount of time using specific programs. Usually is comfortable and familiar with the system operation. March 06 Interface Design 14 Casual system user Only uses on an occasional basis. They may never be truly comfortable with the system. General Human Engineering Guidelines Several situations require some type of feedback:- Tell user what the system expects right now. Tell user whether data is entered correctly or incorrectly. Provide a reason for delay in system processing. Indicate whether or not a task has been successfully completed. System should always know what to do next. Provide instructions (help) on how to proceed, March 06back up, exit etc. Interface Design 15 March 06 Interface Design 16 Within the body zone, the dialogue should be limited to one idea per frame True whether paging or scrolling is used throughout the zone. Display one menu, one input, one report or one query response. March 06 Interface Design 17 Messages, instructions or information should remain in the zone long enough to allow the user to read them Data should not scroll out of the zone before it is read. Display only as much as the area can contain. Use display attributes sparingly Blinking, highlighting etc. March 06 Interface Design 18

4 Simplify complex functions and reduce typing by providing function keys F1 - help Default values for fields and answers should be specified Placing default values in brackets after a text field. Fill in the default value when user tabs to field. March 06 Interface Design 19 Anticipate the errors that users might make Are you sure you want to delete that file? Are you really sure? Also need to consider tone and terminology used in the interface. March 06 Interface Design 20 Dialogue Tone Should be user friendly (rarely achieved). Use simple grammatically correct sentences. Don t be funny, cute or condescending. Terminology Don t use computer jargon. Avoid abbreviations. Terminology Use simple terms. not correct instead of incorrect allows less chance of misspelling or misinterpretation. Be consistent in the use of terminology. Use only edit or modify throughout. Carefully phrase instructions, use action verbs. Select instead of Pick, Type instead of Enter. March 06 Interface Design 21 March 06 Interface Design 22 A number of strategies employed when designing user interfaces:- Menu Selection This is the most popular dialogue strategy. List of alternatives, user selects desired option (using mouse, function keys etc). More sophisticated technology allows touch screen option and pens to name a few. March 06 Interface Design 23 Menu Selection With a lot of alternatives, the menu screen may become too small, then arrange menus hierarchically. Small lists of related items are grouped together in a single menu. Menu driven systems are useful for casual or semi-casual users. Items should be self-explanatory and should contain neither jargon or vague abbreviations of statements. March 06 Interface Design 24

5 Instruction Sets Instead of, or in addition to, menus, design a dialogue around an instruction set Command Language Interface User must learn syntax of this instruction set - suitable only for dedicated users. Three types of syntax that can be defined structured English, mnemonic syntax, natural language syntax March 06 Interface Design 25 Structured English Set of commands that control the system. Elaborate Help system should be created to aid user. Mnemonic syntax Built around meaningful abbreviations of all commands. March 06 Interface Design 26 Natural language syntax User enters command in natural English. System interprets command against a known syntax. Requests clarification if necessary. Question-answer dialogues Supplement the others. simplest questions involve yes or no answers March 06 Interface Design 27 Graphics Provide a means for output and more user friendly interfaces. Most icons suggest their function (cut, paste, delete). March 06 Interface Design 28