User friendly interface
Usable system is the system that allows users to perform tasks they need. Usability is a system property that can be designed and assessed, by involving potential users in the design process.
Usability is a very important but not the only design factor, which is oriented at users' needs. Users of the system must be able to perform their tasks correctly in the systems they work with (e.g. in a bank, in a railway terminal). But it turned out that users often prefer to use systems that are obviously less usable. Factors that influence that are discussed on the last hierarchy level.
ISO (International Standartization Organization) defines usability through a combination of three factors:
- Efficiency: can representatives of the target audience achieve their goals with the help of the system?
- Productivity: which additional resources (e.g. time, mental and physical resources) do users need to achieve their goals?
- Satisfaction: do users find the system comfortable and pleasant?
These criteria are described in ISO 9241 standard. It's important to mention that a product can not have some sort of inner usability. For instance we cannot say that "This cell phone has perfect usability". We can talk about more or less usable product which is used by certain users to perform certain tasks. Besides, newcomers study usable systems quicker and easier, and better remember basic principles of working with the system.
Methods we use to create usable systems
- Task analyses
- Conformity of interface with reccomendations and check-lists
- Expert evaluation
- Interface testing with real users
- United work on the design
If the product is usable it does not mean that people will use it. In order to be used the product should conform with the requirements of our last hierarchy level.