Usability addresses the relationship between tools and their users.
In order for a tool to be effective, it must allow intended users to accomplish
their tasks in the best way possible. The same principle applies to computers,
websites, and other software. In order for these systems to work, their users
must be able to employ them effectively.
Usability depends on a number of factors including how well the functionality
fits user needs, how well the flow through the application fits user
tasks, and how well the response of the application fits user expectations.
We can learn to be better user interface designers by learning design principles
and design guidelines. But even the most insightful designer can only create
a highly-usable system through a process that involves getting information from
people who actually use the system. Usability is the quality of a system that
makes it easy to learn, easy to use, easy to remember, error tolerant, and
subjectively pleasing.
From the user's perspective usability is important because it can make the
difference between performing a task accurately and completely or not, and
enjoying the process or being frustrated. From the developer's perspective
usability is important because it can mean the difference between the success
or failure of a system. From a management point of view, software with poor
usability can reduce the productivity of the workforce to a level of performance
worse than without the system. In all cases, lack of usability can cost time and
effort, and can greatly determine the success or failure of a system. Given a choice,
people will tend to buy systems that are more user-friendly.
The key principle for maximizing usability is to employ iterative design, which
progressively refines the design through evaluation from the early stages of design.
The evaluation steps enable the designers and developers to incorporate user and
client feedback until the system reaches an acceptable level of usability.
The preferred method for ensuring usability is to test actual users on a working
system. Achieving a high level of usability requires focusing design efforts on the
intended end-user of the system. There are many ways to determine who the primary
users are, how they work, and what tasks they must accomplish. However, clients'
schedules and budgets can sometimes prevent this ideal approach. Some alternative
methods include user testing on system prototypes, a usability inspection conducted
by experts, and cognitive modeling.
Usability is one of the focuses of the field of Human-Computer Interaction. As the
name suggests, usability has to do with bridging the gap between people and machines.
A user interface (or human-computer interface) refers to the parts of a hardware and/or
software system that allow a person to communicate with it. This includes output devices
(the way the computer talks to a user) and input devices (the way a user talks to the
computer). Typical "output devices" include computer monitors and the windowing systems
that run on them, but also include speakers and other devices that provide feedback.
"Input devices" include peripherals like keyboards, mice, and joysticks, but also
include microphones and even eye movement devices. Each of these interface components
has devices corresponding to the visual (sight), aural (sound), and haptic (touch)
channels of the brain. Usability engineering studies these elements of the user's
experience.
There are usability courses
offered in a variety of usability areas, from introductory to advanced tutorials,
and including user testing, graphic design, and prototyping techniques. Special topics
include website design and groupware.
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