在电脑编程中，作用域（scope，或译作有效范围）是名字（name）与实体（entity）的绑定（binding）保持有效的那部分计算机进程。不同的编程语言可能有不同的作用域和名字解析。而同一语言内也可能存在多种作用域，随实体的类型变化而不同。作用域类别影响变量的绑定方式，根据语言使用静态作用域还是动态作用域变量的取值可能会有不同的结果。

命名空间是一种作用域，使用作用域的封装性质去逻辑上群组起关相的众识别子於单一识别子之下。因此，作用域可以影响这些内容的名字解析。

程序员常会缩进他们的源代码中的作用域，改善可读性。

In computer programming, the scope of a name binding – an association of a name to an entity, such as a variable – is the part of a computer program where the binding is valid: where the name can be used to refer to the entity. In other parts of the program the name may refer to a different entity (it may have a different binding), or to nothing at all (it may be unbound). The scope of a binding is also known as the visibility of an entity, particularly in older or more technical literature – this is from the perspective of the referenced entity, not the referencing name. A scope is a part of a program that is or can be the scope for a set of bindings – a precise definition is tricky (see below), but in casual use and in practice largely corresponds to a block, a function, or a file, depending on language and type of entity. The term "scope" is also used to refer to the set of all entities that are visible or names that are valid within a portion of the program or at a given point in a program, which is more correctly referred to as context or environment.