Local variable: Difference between revisions

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In [[computer science]], a '''local variable''' is a [[variable]] that is given ''local [[scope (programming)|scope]]''. Such a variable is accessible only from the [[Subroutine|function]] or [[block]] in which it is declared. Local variables are contrasted with [[global alpha beta segato it. In most languages, these local parameters are treated the same as other local variables within the subroutine. In contrast, ''[[call by reference]]'' and ''[[call by name]]'' semantics allow the parameters to act as aliases of the values passed as arguments, allowing the subroutine to modify variables outside its own scope.

In most languages, local variables are [[automatic variable]]s stored on the [[call stack]] directly. This means that when a [[Recursion (computer science)|recursive function]] calls itself, local variables in each instance of the function are given separate memory [[address space]]. Hence variables of this scope can be declared, written to, and read, without any risk of [[Side-effect (computer science)|side-effects]] to processes outside of the block in which they are declared.

Programming languages that employ ''[[call by value]]'' semantics provide a called subroutine with its own local copy of the [[function argument|arguments]] passed to it. In most languages, these local parameters are treated the same as other local variables within the subroutine. In contrast, ''[[call by reference]]'' and ''[[call by name]]'' semantics allow the parameters to act as aliases of the values passed as arguments, allowing the subroutine to modify variables outside its own scope.

Some advocate that all variables should be of local scope to avoid issues with [[Side-effect (computer science)|side-effects]].