programming-for-dummies

Declaring Constants 579
Declaring decimal data types
Decimal values are numbers such as 1.88 or –91.4. Just as you can limit the
range of integer values a variable can hold, so can you limit the range of decimal
values a variable can hold. In Visual Basic, the four types of decimal
data types are Single, Double, Currency, and Extended, as shown in
Table 4-2.
Table 4-2
Pascal Decimal Data Types
Data Type Number of Bytes Range
Single 4 1.5 E–45 to 3.4 E38
Double 8 5.0 E–324 to 1.7 E308
Currency 8 -922,337,203,685,477.5808 to
922,337,203,685,477.5807
Extended 10 3.4 E–4932 to 1.1 E4932
Book VI
Chapter 4
Pascal and Delphi
To declare a variable as a decimal data type, use the Single, Double,
Currency, or Extended keyword, such as
Var
Variablename1 : Single;
Declaring Boolean values
Besides storing text and numbers, variables can also hold a Boolean value —
True or False. To declare a variable to hold a Boolean value, use the
Boolean keyword as follows:
Var
Variablename1 : Boolean;
Declaring Constants
Constants always represent a fixed value. In Pascal, you can declare a constant
and its specific value as follows:
Const
Constantname1 = value;
So if you wanted to assign 3.14 to a pi constant, you could do this:
Const
pi = 3.14;