Persistence
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Persistence may refer to:
- in computer science, to describe a capability used by a computer programmer to store data structures in non-volatile storage such as a file system or a relational database. Without this capability data structures only exist in memory, and will be lost when a program exits. Persistence allows, for example, a program to be restarted and reloaded with the data structures from a previous invocation of the program. Design patterns solving this problem are container based persistence, component based persistence and the Data Access Object model. Examples of persistence are using Java serialization to store Java objects on disk or using J2EE to store Enterprise Java Beans in a relational database.
- In computer programming, persistence also means the ability to retain previous versions of a data structure after it is modified; see persistent data structure.
- Persistence also means how long a CRT's phosphors glow, or remain lit, after they have been struck by electrons from the CRT's electron gun. Older computer monitors ("green screens") had a long persistence, leading to a visual effect called ghosting.
- In mathematics, the additive or multiplicative persistence of a number is how often one has to replace that number with the sum or product of its digits until one arrives at a single digit.
- in environmental engineering, compounds that accumulate and do not easily degrade are called persistent, as in Persistent Organic Pollutant.