Revised(5) Report on the Algorithmic Language Scheme - Literal expressions

### 4.1.2 Literal expressions

    Syntax:  (quote <datum>)
    Syntax:  '<datum>
    Syntax:  <constant>

(quote <datum>) evaluates to <datum>. <Datum> may be any external representation of a Scheme object (see section 3.3). This notation is used to include literal constants in Scheme code.

      (quote a)                     =>  a
      (quote #(a b c))              =>  #(a b c)
      (quote (+ 1 2))               =>  (+ 1 2)

(quote <datum>) may be abbreviated as '<datum>. The two notations are equivalent in all respects.

      'a                   =>  a
      '#(a b c)            =>  #(a b c)
      '()                  =>  ()
      '(+ 1 2)             =>  (+ 1 2)
      '(quote a)           =>  (quote a)
      "a                  =>  (quote a)

Numerical constants, string constants, character constants, and boolean constants evaluate "to themselves"; they need not be quoted.

      '"abc"     =>  "abc"
      "abc"      =>  "abc"
      '145932    =>  145932
      145932     =>  145932
      '#t        =>  #t
      #t         =>  #t

As noted in section 3.4, it is an error to alter a constant (i.e. the value of a literal expression) using a mutation procedure like set-car! or string-set!.