An expression is a combination of basic elements which, on evaluation, yields a result of a given type (for example, Boolean, real, integer, or string). All variables must be explicitly declared before they are used in an expression.

The expressions in this section are grouped into Boolean, integer, real, string, and mnemonic expressions, according to the type of result they return.

Expressions that enable only constant values (no variables) are described under Constant Expressions later in this section.