An expression is a combination of one or more operands, zero or more operators, and zero or more pairs of parentheses.
There are three kinds of expressions:
An arithmetic expression evaluates to a single arithmetic value.
A character expression evaluates to a single value of type character.
A logical or relational expression evaluates to a single logical value.
The operators indicate what action or operation to perform.
The operands indicate what items to apply the action to. An operand can be any of the following kinds of data items:
Constant
Variable
Array element
Function
Substring
Structured record field (if it evaluates to a scalar data item)
An expression