Constants

Constants are identifiers that represent literals or constant expressions 
that can not be changed after they are defined.

For example, Const PI = 3.1415926535897932 will always mean that the 
identifier PI refers to the number 3.1415926535897932.  The identifier PI 
can be used instead of repeating the full number in source.

Global constants once defined, are available globally and the identifier 
can be used to refer to the constant anywhere in the source program. 

After an identifier is defined with the KeyPgConstConst statement, the symbol cannot 
be altered. If code tries to alter a constant, an error message will result 
upon code compilation.

Built-in constants include the KeyPgBooleanBoolean data type values KeyPgTrueTrue and KeyPgFalseFalse.

A constant definition differs from a variable definition.  Variables hold 
values that can be changed.

Example
	Declare Sub PrintConstants ()

	Const FirstNumber = 1
	Const SecondNumber = 2
	Const FirstString = "First string."
	Const FirstBoolean = False
	Const SecondBoolean = True

	Print FirstNumber, SecondNumber 'This will print 1      2
	Print FirstString 'This will print First string.
	Print FirstBoolean, SecondBoolean 'This will print false      true
	Print

	PrintConstants ()

	Sub PrintConstants ()
	   Print FirstNumber, SecondNumber 'This will also print 1        2
	   Print FirstString 'This will also print First string.
	   Print FirstBoolean, SecondBoolean 'This will also print false      true
	End Sub

See also
	* ProPgConstantExpressionsConstant Expressions
	* ProPgLiteralsLiterals
	* KeyPgConstConst
	* KeyPgEnumEnum

