HUMAN-COMPUTER INTERACTION
SECOND EDITION
HUMAN-COMPUTER INTERACTION
SECOND EDITION
In most multimedia systems and in web browsers, virtually all actions take only a single click of the mouse button. You may point at a city on a map and when you click a window opens, showing you tourist information about the city. You may point at a word in some text and when you click you see a definition of the word. You may point at a recognizable iconic button and when you click some action is performed.
The point-and-click style has been popularized by World Wide Web pages, which incorporate all the above types of point-and-click navigation: highlighted words, maps and iconic buttons.
These mechanisms overlap with other interaction styles, especially the use of sculptured elements in WIMP interfaces. However, there is a distinct interaction style for 3D interfaces in that they invite us to use our tacit abilities for the real world, and translate them into the electronic world. Novice users must learn that
Buttons are individual and isolated regions within a display that can be selected by the user to invoke specific operations. These regions are referred to as buttons because they are purposely made to resemble the push buttons you would find on a control panel. 'Pushing' the button invokes a command, the meaning of which is usually indicated by a textual label or a small icon. Buttons can also be used to toggle between two states, displaying status information such as whether the current font is italicized or not in a word processor. Such toggle buttons can be grouped together to allow a user to select one feature from a set of mutually exclusive options, such as the size in points of the current font. These are called radio buttons, since the collection functions much like the old-fashioned mechanical control buttons on car radios. If a set of options is not mutually exclusive, such as font characteristics like bold, italics and underlining, then a set of toggle buttons can be used to indicate the on/off status of the options. This type of collection of buttons is sometimes referred to as check boxes.
It is not possible to cover all of graphic design in a single section, but we can look at a few examples. One of the worst features in many interfaces is the appalling use of colour. This is partly because many monitors only support a limited range of primary colours and partly because, as with the overuse of different fonts in word processors, the designer got carried away. Aside from issues of good taste an overuse of colour can be distracting and, remembering from Chapter 1 that a significant proportion of the population are colour blind, may mean that parts of the text are literally invisible to some users. In general, colour should be used sparingly and not relied upon to give information, but rather to reinforce other attributes.
On a more positive note, careful application of aesthetic concepts can also aid comprehensibility. An example of this is the idea of the counter. This is the gap between the foreground elements: between the letters in text or between the figures and buildings in a painting. Often the shape of the counter is the most important part of the composition of a painting and in calligraphy and typography the balance of a word is determined by giving an even weight to the counters. If one ignores the 'content' of a screen and instead concentrates on the counter, the space between the elements, one can get an overall feel for the layout. If elements that are supposed to be related look separate when you focus on the counter, then something is wrong. Screwing up your eyes so that the screen becomes slightly blurred is another good technique for taking your attention away from the content and looking instead at the broad structure.
If you travel to different countries, you frequently see a document being word processed, where the text of the document and the file names are in the local language, but all the menus and instructions are still in English. The process of making software suitable for different languages and cultures is called localization or internationalization.
It is clear that words have to change and many interface construction toolkits make this easy by using resources. When the program uses names of menu items, error messages and other text, it does not use the text directly, but instead uses a resource identifier, usually simply a number. A simple database is constructed separately that binds these identifiers to particular words and phrases. A different resource database is constructed for each language, and so the program can be customized to use in a particular country by simply choosing the appropriate resource database.
Many of the ideas that Engelbart's team developed at the Augmentation Research Center -- such as word processing and the mouse -- only attained mass commercial success decades after their invention. A live demonstration of his oNLine System (NLS, also later known as NLS/Augment) was given in the autumn of 1968 at the Fall Joint Computer Conference in San Francisco before a captivated audience of computer sceptics. We are not so concerned here with the interaction techniques which were present in NLS, as many of those will be discussed later. What is important here is the method that Engelbart's team adopted in creating their very innovative and powerful interactive systems with the relatively impoverished technology of the 1960s.
Very few will debate the value of a good metaphor for increasing the initial familiarity between user and computer application. The danger of a metaphor is usually realized after the initial honeymoon period. When word processors were first introduced, they relied heavily on the typewriter metaphor. The keyboard of a computer closely resembles that of a standard typewriter, so it seems like a good metaphor from which to start. However, the behaviour of a word processor is different from any typewriter. For example, the space key on a typewriter is passive, producing nothing on the piece of paper and just moving the guide further along the current line. For a typewriter, a space is not a character. However, for a word processor, the blank space is a character which must be inserted within a text just as any other character is inserted. So an experienced typist is not going to be able to predict correctly the behaviour of pressing the spacebar on the keyboard by appealing to her experience with a typewriter. Whereas the typewriter metaphor is beneficial for providing a preliminary understanding of a word processor, the analogy is inadequate for promoting a full understanding of how the word processor works. In fact, the metaphor gets in the way of the user understanding the computer.
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