Predefined

Predefined refers to elements that are defined, established, or supplied in advance by a system, standard, or author, rather than created or configured by a user at runtime. Predefined items are fixed or pre-installed items that are available for use immediately, often to ensure consistency, compatibility, or efficiency. The term is frequently contrasted with user-defined, custom, or dynamic items that are created or determined during operation.

In computing, predefined values and identifiers appear in many contexts. Predefined constants in programming languages are provided by compilers or libraries, such as mathematical constants or system values. Reserved keywords are predefined identifiers that cannot be used as names by programmers. Predefined formats, schemas, templates, and user interface options constrain input and behavior to a sanctioned set. Some systems expose predefined endpoints or capabilities to simplify integration and maintain interoperability.

Advantages of predefined elements include consistency, predictability, and reduced development effort, since common needs are satisfied without new definitions. They can improve reliability and security by using well-tested, documented options. Disadvantages include reduced flexibility, potential mismatch with local requirements, and the risk of stale definitions if standards evolve. Projects must balance the convenience of predefined choices against the need for customization.

See also predefined constant, reserved word, default value, standard library.