Code Consists of Expressions

Like Lisp, Scheme is written as prefix expressions, with parentheses for grouping. Prefix means that the name of an operation comes first, before its operands (the things it operates on).

In Scheme, there's no distinction between expressions (like arithmetic operations) and statements (like an if or a loop or a declaration). They're all "expressions"---it's a very general term.

• Prefix Expressions: Parenthesized prefix expressions
• Values and Side Effects: Expressions return values, but may have side effects
• Defining Variables and Procedures: Defining variables and procedures
• Definitions vs. Assignments: Definitions name storage, assignment changes stored values
• Most Operators are Procedures: Most operators are procedures
• Special Forms: Special forms are not procedures
• Control Structures are Expressions: Control structures are expressions that return values