Boolean Logic

Logical Operators

Comparison Operators

Truth tables

Boolean Logic

• The Boolean values (named after mathematician George Boole)

are TRUE and FALSE.• They can be established in a number of

ways:– Assertion– Boolean Expression– Comparison

Assertion

To assert means to state.

VB example:

Dim Flag As Boolean

Flag = True

Boolean Expression

Logical operators can be used to construct Boolean expressions from Boolean values.

The operands (arguments) must be Boolean.

Not unary, prefix

And dyadic, infix

Or dyadic, infix

Xor dyadic, infix

NOT

Dim Flag As Boolean

Flag = True

Flag = Not Flag

AND

Dim IsNiceWeather As BooleanDim HaveMoney As BooleanDim GoSkiing As BooleanGoSkiing = IsNiceWeather And HaveMoney

OR

Dim GoodBand As Boolean

Dim HotDate As Boolean

Dim GoOut As Boolean

GoOut = GoodBand Or HotDate

XOR

Dim Cookie As Boolean

Dim Candy As Boolean

Dim MomSays As Boolean

MomSays = Cookie Xor Candy

Comparison (= <> <= >= > <)

Comparison Operators are used to establish relationships between Boolean values.

All operators are dyadic, infix.Their arguments can be of any data type, but

must be similar, i.e. both Boolean,both numeric,both String.

Comparison (= <> <= >= > <)

Dim X As Double

Dim Y As Integer

Dim Name1 As String

Dim Name2 As String

Dim Result As Boolean

Result = Name1 < Name2

Result = X = Y

Arithmetic Operators(review)

• exponentiation• multiplication• division (real)• division (integer quotient)• division (integer remainder) • addition• Subtraction

^

*

/

\

Mod

+

-

Other Operators (in order of precedence)

Concatenation &, +

Comparison = <> <= >= > <

Logical Not

And

Or

Xor

Assignment =