Boolean Tags and Boolean Variables

By default, Boolean variables in VBScript are handled differently than Boolean tags are handled in IWS. The Boolean states of FALSE and TRUE have the same meaning, but the numeric values of TRUE are different, as shown in the table below.

Boolean State	Numeric Value in…
Boolean State	Project Tag	VBScript Variable
FALSE	0	0
TRUE	1	−1

Note: In VBScript, False and True are also reserved as keywords.

This difference in how Booleans are handled can seriously affect runtime behavior if you use VBScript in your project. Logical and arithmetic operations — especially the NOT operator — could change tag values in unexpected ways.

You can change this behavior, if necessary, by changing your project's runtime settings.

Changing How VBScript Handles Boolean Tags

You can change the way VBScript handles Boolean tags by activating "VB Boolean" mode. To do this, edit your project file (project_name.app) to change the following setting:

[Script]
VBBoolean=value

If VBBoolean is set to 0, then the project will behave as described above: all VBScript functions and operations will read/write a value of −1 for TRUE to Boolean tags. This is the default setting for projects created with InduSoft Web Studio v6.1+SP3 or earlier and then updated to v6.1+SP4, in order to maintain backward compatibility.

If VBBoolean is set to 1, then VBScript — as it is implemented within IWS — will read/write a value of 1 for TRUE to Boolean tags. (This does not affect Integer or Real tags.) This is the default setting for projects created with InduSoft Web Studio v6.1+SP4 or later.

Note: Be careful when defining a custom property on a Linked Symbol using the #Label:@Pointer syntax. For example:

'The following statements are valid
If $MyBoolean = 1 Then
End If

If $MyBoolean = True Then
End If

If #Mne:@MyPointer = True Then
End If

'The following statement is invalid
If #Mne:@MyPointer = 1 Then
End If