vars

Vars, short for variables, are named storage locations in a program that hold data used during execution. Each variable has a name, a data type in many languages, a scope that limits where it can be accessed, and a lifetime that describes how long it exists.

Typing and declaration vary by language. In statically typed languages the type is fixed at compile time, while in dynamically typed languages the type is associated with the value and can change. Variables may be declared with an explicit type or inferred from an initializer. Some languages allow implicit declarations, while others require you to declare before use.

Mutability and scope are central properties. Many languages distinguish mutable bindings from immutable ones. Scope rules determine where a variable is visible: block or function scope is common, with some languages offering global or module scope. Shadowing can allow an inner scope to re-declare a variable with the same name, temporarily hiding the outer one.

Memory and semantics differ as well. Assigning to a variable updates its binding. Some languages use value semantics, others use references or pointers, affecting how data is stored and copied. Garbage collection or manual memory management may influence lifetime and performance.

Common usage and examples. The keyword var appears in several languages to declare a variable. In JavaScript, var creates a function-scoped binding, while languages such as Go use var with an explicit type. Kotlin uses var for mutable bindings (and val for immutable), whereas Python creates variables through simple assignment without a separate declaration keyword.