variables

Variables are symbols that represent quantities or data values. In mathematics, a variable denotes a value that can change, such as x in an equation. In computing, a variable is a name associated with a storage location that holds a value during program execution.

In programming languages, a variable combines a name, a storage location, and a value. The value can typically be read and replaced through assignment. Variables have types that describe the kind of data they hold, and many languages distinguish between mutable and immutable bindings.

Scope determines where a variable can be accessed: local variables are visible only within a block or function, while global variables are accessible throughout a program. Lifetimes describe when storage is allocated and released, such as per call or for the duration of a program. Most languages are case sensitive, require valid identifiers, and follow rules about starting characters and allowed symbols.

Initialization is the process of giving a variable its first value. Some languages require it before use; others provide defaults. Constants or final variables may be defined to prevent changes after initialization. Common pitfalls include using uninitialized variables, shadowing names in inner scopes, and type errors when values are assigned to incompatible variables.