Ordinal Types

   INTEGER | CARDINAL | BOOLEAN | CHAR        (* built-in   *)
            | "{" id "," id "," ... "}"       (* enumerated *)
            | "[" lo..hi "]"                  (* subrange   *)

Ordinal types denote sets of values in each of which has a unique successor.

INTEGER

The set of signed integers (positive and negative).

CARDINAL

A synonym for the subrange [0..LAST(INTEGER)]

BOOLEAN

The enumeration {FALSE, TRUE}

CHAR

The set of ISO-Latin-1 characters (an extension of ASCII)

Enumerated

An enumerated type is an ordered set of values whose names are specified by the user, as follows:

TYPE Day = {Sunday, Monday, Tuesday, Wednesday, Thursday,
            Friday, Saturday};

Values of an enumeration are specified as type-name.value, for example, Day.Sunday rather than just Sunday. Thus, you should keep enumeration type names short.

Subrange

A subrange is a subset of the values of the base type specified by the range lo..hi. Values lo and hi must have the same ordinal type. Integer subranges are the most common:

TYPE Digit = [0 .. 9];                       (* subrange of INTEGER *)
     WeekDay = [Day.Monday .. Day.Friday];   (* subrange of Day *)