Used to indicate an uninitialized variable value. A variable value is uninitialized when it is first created and no value is assigned to it, or when a variable value is explicitly set to empty.
Note: This is not the same as Null!!
Used to test if a variable is uninitialized.
Example: If (IsEmpty(x)) 'is x uninitialized?
|Nothing||Used to indicate an uninitialized object value, or to
disassociate an object variable from an object to release system resources.
Example: Set myObject=Nothing
|Is Nothing||Used to test if a value is an initialized object.
Example: If (myObject Is Nothing) 'is it unset?
Note: If you compare a value to Nothing, you will not get the right result! Example: If (myObject = Nothing) 'always false!
|Null||Used to indicate that a variable contains no valid data.
One way to think of Null is that someone has explicitly set the value to "invalid", unlike Empty where the value is "not set".
Note: This is not the same as Empty or Nothing!!
Example: x=Null 'x contains no valid data
|IsNull||Used to test if a value contains invalid data.
Example: if (IsNull(x)) 'is x invalid?
|True||Used to indicate a Boolean condition that is correct (True has a value of -1)|
|False||Used to indicate a Boolean condition that is not correct (False has a value of 0)|