This section contains information about expressions. The expressions are presented in alphabetical order.

An expression describes how a value can be obtained by applying specified operations to designated operands or primaries.

<expression>

──┬─<arithmetic expression>───────┬────────────────────────────────────┤
  ├─<bit manipulation expression>─┤
  ├─<Boolean expression>──────────┤
  ├─<case expression>─────────────┤
  ├─<complex expression>──────────┤
  ├─<conditional expression>──────┤
  ├─<designational expression>────┤
  ├─<function expression>─────────┤
  ├─<null value>──────────────────┤
  ├─<pointer expression>──────────┤
  └─<string expression>───────────┘

The evaluation of each expression returns a different value, as follows:

A bit manipulation expression operates on bits within words and makes it possible to build the contents of a word from groups of bits contained in other words.

Case expressions and conditional expressions allow one of several alternative expressions to be chosen for evaluation based on a selection value.

A function expression is a call on a typed procedure. The procedure can be declared in the program or it can be an intrinsic which is a typed procedure that is a predefined part of the ALGOL language. Intrinsic functions exist that are predefined arithmetic expressions, predefined Boolean expressions, predefined complex expressions, predefined pointer expressions, and predefined string expressions. For example, SQRT(<arithmetic expression>) is a function expression that returns the square root of the value of <arithmetic expression> construct. Because the SQRT returns a numeric value, it is an arithmetic function, a predefined arithmetic expression.