TOPS-20 PASCAL Language Manual - Bitsavers

PASCAL DATA TYPES
You can use strings such as 'HELLO' and '****', but you must represent
them as packed arrays of characters (see Section 2.3.1.2). When you
use the ORD function in an expression of type CHAR, the result is the
ordinal value in the ASCII character set of the character value. See
Section 2.2.2.3 for an explanation of the ORD function.
2.2.2 User-Defined Scalar Data Types
User-defined scalar data types are those that you define, as opposed
to those data types that PASCAL predefines for you. PASCAL allows you
to define two kinds of scalar data types: enumerated and subrange.
An enumerated type consists of an ordered list of identifiers. The
subrange type is a continuous range of values of a defined scalar
type, called a base type. The following sections describe these two
user-defined types.
2.2.2.1 Enumerated Data Types - An enumerated data type is an ordered
list of identifiers. To define an enumerated type, list in some order
all the identifiers denoting its values. With PASCAL, you can define
an enumerated data type in two ways:
Fo rma t I
Fo rma t 2
where:
TYPE identifier (identifier II,identifier, •.• ] )
VAR identifier (identifier I[ ,identifier, •.• ] )
identifier
is the name of the enumerated type.
For example:
TYPE Beverage = (Milk, Water, Cola, Beer);
This TYPE section defines the type Beverage and lists all the
that Beverage can assume within a program.
values
PASCAL assigns an order to the items in your list from left to right.
Thus, the values of an enumerated type follow a left-to-right order,
so that the last value in the list is greater than the first, for
example:
TYPE Seasons = (Spring, Summer, Fall, Winter) ,
The relational expression (Spring < Fall)
precedes Fall in the list of values.
is TRUE because Spring
The only restriction on the values of an enumerated type is that you
cannot define the same value in more than one list in the same TYPE
section. For example, the following is illegal:
TYPE Seasons = (Spring, Summer, Fall, Winter)
School~ear = (Fall, Winter, Spring);
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