FreeBasic Boolean Keyword

last modified June 16, 2025

The FreeBasic Boolean keyword represents a data type that can hold only two values: true or false. Boolean values are fundamental for controlling program flow and making logical decisions.

Basic Definition

In FreeBasic, Boolean is a built-in data type that occupies 1 byte of memory. It can only contain the values true (non-zero) or false (zero).

Boolean variables are commonly used in conditional statements, loops, and logical operations. They make code more readable when dealing with yes/no or on/off scenarios.

Declaring Boolean Variables

This example shows how to declare and initialize Boolean variables.

boolean_declare.bas

Dim isReady As Boolean
Dim hasPermission As Boolean = True
Dim isComplete As Boolean = False

Print "isReady: "; isReady
Print "hasPermission: "; hasPermission
Print "isComplete: "; isComplete

Here we declare three Boolean variables. The first is uninitialized and defaults to false. The others are explicitly set to true and false. FreeBasic prints 0 for false and -1 for true when displaying Boolean values.

Boolean in Conditional Statements

Boolean values are most commonly used to control program flow in conditionals.

boolean_conditional.bas

Dim isLoggedIn As Boolean = True

If isLoggedIn Then
    Print "Welcome back, user!"
Else
    Print "Please log in to continue."
End If

This example demonstrates using a Boolean variable in an If statement. The condition evaluates to true, so the welcome message is printed. Boolean variables make conditional logic more readable.

Boolean Operators

FreeBasic provides logical operators for combining Boolean values.

boolean_operators.bas

Dim hasAccount As Boolean = True
Dim isVerified As Boolean = False

Print "AND: "; hasAccount And isVerified
Print "OR: "; hasAccount Or isVerified
Print "NOT: "; Not hasAccount
Print "XOR: "; hasAccount Xor isVerified

This code demonstrates Boolean operators: AND, OR, NOT, and XOR. The AND operator returns true only if both operands are true. OR returns true if either operand is true. NOT inverts the value.

Boolean Function Return Values

Functions can return Boolean values to indicate success or failure.

boolean_function.bas

Function IsEven(n As Integer) As Boolean
    Return (n Mod 2) = 0
End Function

Dim number As Integer = 42
If IsEven(number) Then
    Print number; " is even"
Else
    Print number; " is odd"
End If

The IsEven function returns a Boolean indicating whether a number is even. This makes the calling code very readable, as the function name clearly expresses its purpose and return type.

Boolean Arrays

Arrays of Boolean values can be useful for tracking multiple true/false states.

boolean_array.bas

Dim weekdays(1 To 7) As Boolean
weekdays(2) = True  ' Monday
weekdays(3) = True  ' Tuesday
weekdays(5) = True  ' Thursday

For i As Integer = 1 To 7
    Print "Day "; i; ": "; IIf(weekdays(i), "Working day", "Off day")
Next

This example creates an array to track which days are workdays. We set some days to true and others remain false by default. The IIf function helps display meaningful strings based on the Boolean values.

Boolean with Comparison Operators

Comparison operations naturally result in Boolean values.

boolean_comparison.bas

Dim a As Integer = 10
Dim b As Integer = 20

Dim result As Boolean = (a < b)

Print "a < b: "; result
Print "a = b: "; (a = b)
Print "a > b: "; (a > b)

Here we store the result of a comparison in a Boolean variable. We also directly print comparison results. All comparisons evaluate to Boolean values in FreeBasic.

Boolean Type Conversion

FreeBasic automatically converts between Boolean and other numeric types.

boolean_conversion.bas

Dim flag As Boolean = True
Dim numericValue As Integer = flag

Print "Boolean to Integer: "; numericValue

Dim newFlag As Boolean = -1
Print "Integer to Boolean: "; newFlag

This demonstrates implicit type conversion. When converting to integer, true becomes -1 and false becomes 0. When converting from integer, any non-zero value becomes true, while zero becomes false.

Best Practices

Initialization: Always initialize Boolean variables explicitly.
Readability: Prefer Boolean variables over magic numbers in conditions.
Functions: Use Boolean return types for yes/no questions.
Operators: Use parentheses to clarify complex Boolean expressions.

This tutorial covered the FreeBasic Boolean keyword with practical examples showing its usage in different scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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