Variable Bindings (MIT/GNU Scheme 12.1)

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#### 1.2.1 Variable Bindings

Any identifier that is not a syntactic keyword may be used as a variable (see Identifiers). A variable may name a location where a value can be stored. A variable that does so is said to be bound to the location. The value stored in the location to which a variable is bound is called the variable’s value. (The variable is sometimes said to name the value or to be bound to the value.)

A variable may be bound but still not have a value; such a variable is said to be unassigned. Referencing an unassigned variable is an error. When this error is signalled, it is a condition of type `condition-type:unassigned-variable`; sometimes the compiler does not generate code to signal the error. Unassigned variables are useful only in combination with side effects (see Assignments).