Human–computer interaction (HCI) involves the study, planning, and design of the interaction between people (users) and computers. It is often regarded as the intersection of computer science, behavioral sciences, design and several other fields of study. The term was popularized by Card, Moran, and Newell 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 (such as a hammer, useful for driving nails, but not much else), a computer has many affordances for use and this takes place in an open-ended dialog between the user and the computer.
Because human–computer interaction studies a human and a machine in conjunction, it draws from supporting knowledge on both the machine and the human side. On the machine side, techniques in computer graphics, operating systems, programming languages, and development environments are relevant. On the human side, communication theory, graphic and industrial design disciplines, linguistics, social sciences, cognitive psychology, and human factors such as computer user satisfaction are relevant. Engineering and design methods are also relevant. Due to the multidisciplinary nature of HCI, people with different backgrounds contribute to its success. HCI is also sometimes referred to as man–machine interaction (MMI) or computer–human interaction (CHI).
A modern notification system is a combination of software and hardware that provides a means of delivering a message to a set of recipients. For example, notification systems can send an e-mail when a new topic has been added to Wikipedia. The complexity of the notification system is often dependent on the types of messages that must be sent. An e-mail noting when a page has been inserted into Wikipedia is adequate for such a straightforward task. However, notifying individuals when a building is on fire would require real-time interaction, escalation, scheduling]disambiguation needed[, rosters, and fail-over scenarios.
To prevent email spam (a.k.a. unsolicited bulk email), both end users and administrators of email systems use various anti-spam techniques. Some of these techniques may have been embedded in products, services and software to ease the burden on users and administrators. No one technique is a complete solution to the spam problem, and each has trade-offs between incorrectly rejecting legitimate email vs. not rejecting all spam, and the associated costs in time and effort.
Anti-spam techniques can be broken into four broad categories: those that require actions by individuals, those that can be automated by email administrators, those that can be automated by email senders and those employed by researchers and law enforcement officials.
A return receipt is a postal service document confirming the arrival of a message or parcel at its intended destination. Internationally, the service is known as avis de réception (AR), but in some English-speaking countries the terms acknowledgement of receipt or advice of receipt are used.