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.
What makes a website or piece of software usable?
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.
Why is Usability Important?
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.
How Do You Achieve a High Level of Usability?
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.
Where is Usability Applied?
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. From http://www.usabilityfirst.com∞
Jacob Nielsen's WebSite∞