page_title: Human–computer interaction
section_title: Principles
hierarchical_section_title: Human–computer interaction / Design / Principles
context_page_description: Human–computer interaction studies the design and use of computer technology, focused on the interfaces between people and computers. Researchers in the field of HCI observe the ways in which humans interact with computers and design technologies that let humans interact with computers in novel ways.
  As a field of research, human–computer interaction is situated at the intersection of computer science, behavioural sciences, design, media studies, and several other fields of study. The term was popularized by Stuart K. Card, Allen Newell, and Thomas P. Moran in their seminal 1983 book, The Psychology of Human–Computer Interaction, although the authors first used the term in 1980 and the first known use was in 1975. The term connotes that, unlike other tools with only limited uses, a computer has many uses and this takes place as an open-ended dialog between the user and the computer. The notion of dialog likens human–computer interaction to human-to-human interaction, an analogy which is crucial to theoretical considerations in the field.
context_section_description: The following experimental design principles are considered, when evaluating a current user interface, or designing a new user interface:
  Early focus is placed on user(s) and task(s): How many users are needed to perform the task(s) is established and who the appropriate users should be is determined (someone who has never used the interface, and will not use the interface in the future, is most likely not a valid user). In addition, the task(s) the users will be performing and how often the task(s) need to be performed is defined.
  Empirical measurement: the interface is tested with real users who come in contact with the interface on a daily basis. The results can vary with the performance level of the user and the typical human–computer interaction may not always be represented. Quantitative usability specifics, such as the number of users performing the task(s), the time to complete the task(s), and the number of errors made during the task(s) are determined.
  Iterative design: After determining what users, tasks, and empirical measurements to include, the following iterative design steps are performed:
  Design the user interface
  Test
  Analyze results
  Repeat
  The iterative design process is repeated until a sensible, user-friendly interface is created.
caption: The user interacts directly with hardware for the human input and output such as displays, e.g. through a graphical user interface. The user interacts with the computer over this software interface using the given input and output (I/O) hardware. 
   Software and hardware are matched, so that the processing of the user input is fast enough, and the latency of the computer output is not disruptive to the workflow.