VBScript Reference Manual for InduSoft Web Studio

VBScript Reference Manual InduSoft Web Studio
Literal Keywords used with Boolean data subtypes
Keyword Description
False Boolean condition that is not correct (false has a value of 0)
True Boolean condition that is correct (true has a value of -1)
An example would be:
Dim overtemp_condition
If $temperature > 100 then
overtemp_condtion = True
Else
Overtemp_condition = False
End If
There are several logical operators available in VBScript that can be used to evaluate logical
expressions. These logical operators can be used with both Boolean data subtypes as well as in
Comparison expressions. In the table below, a and b are assumed to represent logical expressions.
Logical Operators
Logic Operator Example Returns
AND And a AND b True only if a and b are both true
OR Or, | a OR b True if a or b is true, or both are true
Exclusive OR Xor a Xor b True if a or b is true, but not both
Equivalence Eqv a Eqv b True if a and b are the same
Implication Imp a Imp b False only if a is true and b is false otherwise
true
NOT Not a Not b True if a is false; False if a is true
A couple examples of the logical operators are:
Dim temp, pressure
If (temp > 212) And (pressure > 1) then ‘ evaluate a conditional expression
Call Alarm_routine
End If
Dim a, b, temp, pressure
a = (temp > 212) And (pressure > 1) ‘ conditional expression stored as a boolean
If a = True Then ‘ logical condition test
Call Alarm_routine
End If
Note that the | operator (shift \) can be used instead of the Or logical operator. The statements (a | b)
and (a Or b) are equivalent.
Logical Truth Table
a b a And b a Or b a Xor b a Eqv b a Imp b Not a
T T T T F T T F
T F F T T F F F
F T F T T F T T
F F F F F T T T
68 InduSoft, Ltd.