HUMAN-COMPUTER INTERACTION
SECOND EDITION
HUMAN-COMPUTER INTERACTION
SECOND EDITION
Similarly there are a number of effectors, including the limbs, fingers, eyes, head and vocal system. In the interaction with the computer, the fingers play the primary role, through typing or mouse control, with lesser use of speech, and eye and head position.
Imagine using a personal computer (PC) with a mouse and a keyboard. The application you are using has a graphical interface, with menus, icons and windows. (If you are unfamiliar with this technology, skip forward to Chapter 2 where it is described more fully.) In your interaction with this system you receive information primarily by sight, from what appears on the screen. However, you may also receive information by ear: for example, the computer may 'beep' at you if you make a mistake. Touch plays a part too in that you may feel a key depressing or the orientation of the mouse, which provides vital feedback about what you have done. You yourself send information to the computer mainly by hand, either by hitting keys or moving the mouse. Sight and hearing do not play a direct role in sending information in this example, although they may be used to receive information from a third source (for example, a book, or the words of another person) which is then transmitted to the computer.
The first part of this chapter concentrates on the transference of information from the user to the computer and back. We begin by considering a current typical computer interface and the devices it employs (the keyboard and mouse), showing that the design is constrained by and related to the technology used. Since the devices influence the style of interaction, we move on to see the effects of different devices, considering their strong and weak points, and how they might alter the interface and interaction. Then we move on to consider devices that are not in common use, and suggest how they may affect future interfaces.
In addition to direct input and output, information is passed to and fro via paper documents. This is dealt with in Section 2.5, which describes printers and scanners. Although not requiring the same degree of user interaction as a mouse or keyboard, these are an important means of input and output for many current applications.
Consider a typical computer setup as shown in Figure 2.1. There is the computer 'box' itself, a keyboard, a mouse and a colour screen. The screen layout is shown alongside it. If we examine the interface, we can see how its various characteristics are related to the devices used. The details of the interface itself, its underlying principles and design, are discussed in more depth in Chapter 3; we will simply consider the sorts of things that it allows us to do, and the device that facilitates the required actions. Each is discussed in turn, in conjunction with alternatives that offer a different approach to the same situation. The diversity of devices reflects the fact that there are many different types of data that may have to be entered into and obtained from a system, and there are also many different types of user, each with their own unique requirements.
Some organizer designs have dispensed with a keyboard completely. With such systems one must consider all sorts of other ways to interact with the system that are not character based. For example, we may decide to use drawings to tell the system what to do rather than commands using gesture recognition, for example drawing a line through a word in order to delete it. The important point is that a different input device that was initially considered simply as an alternative to the keyboard opens up a whole host of alternative interface designs and different possibilities for interaction. Pen-based systems that use handwriting recognition often use a special pen-based operating system, which attempts to tackle some of the problems of using a pen-based approach to what is otherwise a standard keyboard and mouse-oriented system, in much the same way as we suggested above, although there are also pen-based versions of standard operating systems.
Central to most modern computing systems is the ability to point at something on the screen and thereby manipulate it, or perform some function. There has been a long history of such devices, in particular in computer-aided design (CAD), where positioning and drawing are the major activities. Pointing devices allow the user to point, position and select items, either directly or by manipulating a pointer on the screen. Of these devices, the mouse is most common, if not ubiquitous.
The mouse has become a major component of the majority of personal computer systems and general-purpose workstations sold today, and is the little box with the tail connecting it to the machine in our basic computer system picture (Figure 2.1). It is a small, palm-sized box housing a weighted ball -- as the box is moved over the tabletop, the ball is rolled by the table and so rotates inside the housing. This rotation is detected by small rollers that are in contact with the ball, and these adjust the values of potentiometers. The changing values of these potentiometers can be directly related to changes in position of the ball. The potentiometers are aligned in different directions so that they can detect both horizontal and vertical motion. The relative motion information is passed to the computer via a wire attached to the box, and moves a pointer on the screen, called the cursor. The whole arrangement tends to look rodent-like, with the box acting as the body and the wire as the tail; hence the term 'mouse'. In addition to detecting motion, the mouse has typically one, two or three buttons on top. These are used to indicate selection or to initiate action. Single-button mice tend to have similar functionality to multi-button mice, and achieve this by instituting different operations for a single and a double button click. A 'double-click' is when the button is pressed twice in rapid succession. Multi-button mice tend to allocate one operation to each particular button.
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