What is "side effect"

also side-effect, 1884, from side (adj.) + effect (n.). Medical use, with reference to drugs, is recorded from 1939.

alt. 1 (context idiomatic English) An unintended consequence of any action in addition to the intended consequence of that action. 2 (context idiomatic medicine English) An adverse effect, an unintended consequence of a drug or therapy; usually not a beneficial effect. 3 (context computing English) A change in state caused by a function call (typically "side-effect"). n. 1 (context idiomatic English) An unintended consequence of any action in addition to the intended consequence of that action. 2 (context idiomatic medicine English) An adverse effect, an unintended consequence of a drug or therapy; usually not a beneficial effect. 3 (context computing English) A change in state caused by a function call (typically "side-effect").

1. n. a secondary and usually adverse effect of a drug or therapy; "severe headaches are one of the side effects of the drug"

2. any adverse and unwanted secondary effect; "a strategy to contain the fallout from the accounting scandal" [syn: fallout]

In computer science, a function or expression is said to have a side effect if it modifies some state or has an observable interaction with calling functions or the outside world. For example, a particular function might modify a global variable or static variable, modify one of its arguments, raise an exception, write data to a display or file, read data, or call other side-effecting functions. In the presence of side effects, a program's behaviour may depend on history; that is, the order of evaluation matters. Understanding and debugging a function with side effects requires knowledge about the context and its possible histories.

Side effects are the most common way that a program interacts with the outside world (people, filesystems, other computers on networks). But the degree to which side effects are used depends on the programming paradigm. Imperative programming is known for its frequent utilization of side effects.

In functional programming, side effects are rarely used. The lack of side effects makes it easier to do formal verifications of a program. Functional languages such as Standard ML, Scheme and Scala do not restrict side effects, but it is customary for programmers to avoid them. The functional language Haskell expresses side effects such as I/O and other stateful computations using monadic actions.

Assembly language programmers must be aware of hidden side effects — instructions that modify parts of the processor state which are not mentioned in the instruction's mnemonic. A classic example of a hidden side effect is an arithmetic instruction that implicitly modifies condition codes (a hidden side effect) while it explicitly modifies a register (the overt effect). One potential drawback of an instruction set with hidden side effects is that, if many instructions have side effects on a single piece of state, like condition codes, then the logic required to update that state sequentially may become a performance bottleneck. The problem is particularly acute on some processors designed with pipelining (since 1990) or with out-of-order execution. Such a processor may require additional control circuitry to detect hidden side effects and stall the pipeline if the next instruction depends on the results of those effects.

Side Effect was an American disco and jazz-funk band, that recorded between 1972 and 1982. The group was formed in Los Angeles, California in 1972 by Augie Johnson who became their leader.

A side effect is an effect that is secondary to the one intended. Side effect or side effects may also refer to:

Side Effect is the second album by R&B group Side Effect. Released in 1975, this was their first album for Fantasy Records.