Boolean Values

 Fundamentals of Boolean Values

 The Boolean Data Type
 A value is referred to as Boolean if it can be either true or false. Like a number or a string, a Boolean value can be stored in a variable. To declare such a variable, use the Boolean keyword. Here is an example: ```Public Module Exercise Public Function Main() As Integer Dim EmployeeIsMarried As Boolean Return 0 End Function End Module ```

To actually use a Boolean variable, you can assign a value to it. By default, if you declare a Boolean variable but do not initialized it, it receives a value of False:

```Public Module Exercise

Public Function Main() As Integer
Dim EmployeeIsMarried As Boolean

MsgBox("Employee Is Married? " & EmployeeIsMarried)
Return 0
End Function

End Module```

This would produce:

To initialize a Boolean variable, assign it a True or a False value. In the Visual Basic language, a Boolean variable can also deal with numeric values. The False value is equivalent to 0. For example, instead of False, you can initialize a Boolean variable with 0. Any other numeric value, whether positive or negative, corresponds to True:

```Public Module Exercise

Public Function Main() As Integer
Dim EmployeeIsMarried As Boolean

EmployeeIsMarried = -792730
MsgBox("Employee Is Married? " & EmployeeIsMarried)
Return 0
End Function

End Module```

The number can be decimal or hexadecimal:

```Public Module Exercise

Public Function Main() As Integer
Dim EmployeeIsMarried As Boolean

EmployeeIsMarried = &HFA26B5
MsgBox("Employee Is Married? " & EmployeeIsMarried)
Return 0
End Function

End Module```
 Passing a Boolean Variable as Argument

As done with the other data types we have used so far, a Boolean values can be involved with a procedure. This means that a Boolean variable can be passed to a procedure and/or a function can be made to return a Boolean value.

To pass an argument as a Boolean value, in the parentheses of the procedure, type the name of the argument followed by the As Boolean expression. Here is an example:

```Private Sub CheckingEmployee(ByVal IsFullTime As Boolean)

End Sub```

In the same way, you can pass as many Boolean arguments as you need, and you can combine Boolean and non-Boolean arguments as you judge necessary. Then, in the body of the procedure, use (or don't use) the Boolean argument.

 Returning a Boolean Value

Just as done for the other data types, you can create a function that returns a Boolean value. When declaring the function, specify its name and the As Boolean expression on the right side of the closing parenthesis. Here is an example:

```Public Function IsDifferent() As Boolean

End Function```

Of course, the function can take arguments of any kind you judge necessary:

```Public Function IsDifferent(ByVal Value1 As Integer,
ByVal Value2 As Integer) As Boolean

End Function```

In the body of the function, do whatever you judge necessary. Before exiting the function, you must return a value that evaluates to True or False.