Type Declarations

Abstract

Every variable declaration specifies the variable’s type as its constant property. The type can be one of the standard, primitive types, or it may be of a type declared in the program itself. Type declarations have the form $\$ \quad {\text{TypeDeclaration = identifier = type}}.$ They are preceded by the symbol TYPE Types are classified into unstructured and structured types. Each type essentially defines the set of values which a variable of this type may assume. A value of an unstructured type is an atomic unit, whereas a value of structured type has components (elements). For example, the type CARDINAL is unstructured; its elements are atomic. It does not make sense, e.g. to refer to the third bit of the value 13; the circumstance that a number may “have a third bit”, or a second digit, is a characteristic of its (internal) representation, which intentionally is to remain unknown.