An operator is a special symbol which indicates a certain process is carried out.
Operators in programming languages are taken from mathematics. Programmers work with
data. The operators are used to process data.
We have several types of operators:
The following example shows arithmetic operations.
Next we will show the distinction between normal and integer division.
The last two operators that we will mention are modulo operator and exponentiation operator.
Finally, we will mention exponentiation operator.
Boolean operators are used to work with truth values.
The logical
The logical
The negation operator
Relational operators are also called comparison operators.
Notice that the relational operators are not limited to numbers. We can use them for other objects as well. Although they might not always be meaningful.
Finally, we will mention the
The bitwise negation operator changes each 1 to 0 and 0 to 1.
The bitwise and operator performs bit-by-bit comparison between two numbers. The result for a bit position is 1 only if both corresponding bits in the operands are 1.
Other compound operators are:
We have several types of operators:
- Arithmetic operators
- Boolean operators
- Relational operators
- Bitwise operators
Option Strict On Module Example Sub Main() Print(2) Print(-2) Print(2+2) Print(2-2) End Sub End Module+ and - signs can be addition and subtraction operators as well as unary sign operators. It depends on the situation.
Option Strict On Module Example Dim a As Byte Sub Main() a = 1 Print(-a) ' Prints -1 Print(-(-a)) ' Prints 1 End Sub End ModuleThe plus sign can be used to indicate that we have a positive number. But it is mostly not used. The minus sign changes the sign of a value.
Option Strict On Module Example Dim a As Byte Dim b As Byte Sub Main() a = 3 * 3 b = 2 + 2 Print(a) ' Prints 9 Print(b) ' Print 4 End Sub End ModuleMultiplication and addition operators are examples of binary operators. They are used with two operands.
The assignment operator
The assignment operator = assigns a value to a variable. A variable is a placeholder for a value. In mathematics, the = operator has a different meaning. In an equation, the = operator is an equality operator. The left side of the equation is equal to the right one.x = 1 Print(x) ' Prints 1Here we assign a number to the x variable.
x = x + 1 Print(x)The previous expression does not make sense in mathematics. But it is legal in programming. The expression adds 1 to the x variable. The right side is equal to 2 and 2 is assigned to x.
3 = xThis code example results in syntax error. We cannot assign a value to a literal.
Arithmetic operators
The following is a table of arithmetic operators in Visual Basic.Symbol | Name |
---|---|
+ | Addition |
- | Subtraction |
* | Multiplication |
/ | Division |
\ | Integer Division |
Mod | Modulo |
^ | Exponentiation |
Option Strict On Module Example Dim a As Byte Dim b As Byte Dim c As Byte Dim add As Byte Dim sb As Byte Dim mult As Byte Dim div As Byte Sub Main() a = 10 b = 11 c = 12 add = a + b + c sb = c - a mult = a * b div = CType(c / 3, Byte) Print(add) Print(sb) Print(mult) Print(div) End Sub End ModuleIn the preceding example, we use addition, subtraction, multiplication and division operations. This is all familiar from the mathematics.
33 2 110 4Output of the example.
Next we will show the distinction between normal and integer division.
Option Strict On Module Example Dim a As Single = 5 Dim b As Single = 2 Dim c As Single Sub Main() c = 5 / 2 Print(c) c = 5 \ 2 Print(c) End Sub End ModuleIn the preceding example, we divide two numbers using normal and integer division operator. Visual Basic has two distinct operators for division.
Dim a As Single = 5We use floating point data types.
c = 5 / 2 Print(c)This is the 'normal' division operation. It returns 2.5, as expected.
c = 5 \ 2 Print(c)This is integer division. The result of this operation is always and integer. The c variable has value 2.
2.5 2Result of the division
The last two operators that we will mention are modulo operator and exponentiation operator.
Print(9 Mod 4) ' Prints 1The
Mod
operator is called the modulo operator.
It finds the remainder of division of one number by another.
9 Mod 4
, 9 modulo 4 is 1, because 4 goes into 9
twice with a remainder of 1. Modulo operator can be handy for example
when we want to check for prime numbers.
Finally, we will mention exponentiation operator.
Print(9 ^ 2) ' Prints 819 ^ 2 = 9 * 9 = 81
Concatenating strings
In Visual Basic we have two operators for string concatenation. The plus + operator and the & ampersand operator.Option Strict On Module Example Sub Main() Print("Return " & "of " & "the king") Print("Return " + "of " + "the king") End Sub End ModuleWe join three strings together using both operators.
Return of the king Return of the king
And this is, what we get. Same result for both cases.
Boolean operators
In Visual Basic, we have the following logical operators. Boolean operators are also called logical.Symbol | Name |
---|---|
And | logical conjunction |
AndAlso | short circuit And |
Or | logical inclusion |
OrElse | short circuit Or |
Xor | logical inclusion |
Not | negation |
Option Strict On Module Example Dim x As Byte = 3 Dim y As Byte = 8 Sub Main() Print(x = y) Print(y > x) If (y > x) Print("y is greater than x") End If End Sub End ModuleMany expressions result in a boolean value. Boolean values are used in conditional statements.
Print(x = y) Print(y > x)Relational operators always result in a Boolean value. These two lines print False and True.
If (y > x) Print("y is greater than x") End IfThe body of the
If
statement
is executed only if the condition inside the parentheses
is met. The x > y returns True, so the message "y is greater than x"
is printed to the terminal.
Option Strict On Module Example Dim a As Boolean Dim b As Boolean Dim c As Boolean Dim d As Boolean Sub Main() a = (True And True) b = (True And False) c = (False And True) d = (False And False) Print(a) Print(b) Print(c) Print(d) End Sub End ModuleExample shows the logical
And
operator.
It evaluates to True only if both operands are True.
True False False False
The logical
Xor
operator evaluates to True,
if exactly one of the operands is True.
Option Strict On Module Example Dim a As Boolean Dim b As Boolean Dim c As Boolean Dim d As Boolean Sub Main a = (True Xor True) b = (True Xor False) c = (False Xor True) d = (False Xor False) Print(a) Print(b) Print(c) Print(d) End Sub End ModuleThe logical
Xor
evaluates to False, if
both operands are True or both False.
False True True False
The logical
Or
operator evaluates to True,
if either of the operands is True.
Option Strict On Module Example Sub Main() Dim a As Boolean = True Or True Dim b As Boolean = True Or False Dim c As Boolean = False Or True Dim d As Boolean = False Or False Print(a) Print(b) Print(c) Print(d) End Sub End ModuleIf one of the sides of the operator is True, the outcome of the operation is True.
True True True False
The negation operator
Not
makes True False and False True.
Option Strict On Module Example Sub Main(
) Print(Not True) Print(Not False) Print(Not (4 < 3)) End Sub End ModuleThe example shows the negation operator in action.
False True True
Relational Operators
Relational operators are used to compare values. These operators always result in a boolean value.Symbol | Meaning |
---|---|
< | less than |
<= | less than or equal to |
> | greater than |
>= | greater than or equal to |
== | equal to |
<> | not equal to |
Is | compares references |
Print(3 < 4) ' Prints True Print(3 = 4) ' Prints False Print(4 >= 3) ' Prints TrueAs we already mentioned, the relational operators return boolean values. Note that in Visual Basic, the comparison operator is (=). Not (==) like in C and C influenced languages.
Notice that the relational operators are not limited to numbers. We can use them for other objects as well. Although they might not always be meaningful.
Option Strict On Module Example Sub Main() Print("six" = "six") ' Prints True ' Print("a" > 6) 'this would throw ' an exception Print("a" < "b") ' Prints True End Sub End ModuleWe can compare string objects too. Comparison operators in a string context compare the sorting order of the characters.
Print("a" < "b") ' Prints TrueWhat exactly happens here? Computers do not know characters or strings. For them, everything is just a number. Characters are special numbers stored in specific tables. Like ASCII.
Option Strict On Module Example Sub Main() Print("a" < "b") Print("a is: {0}", Asc("a")) Print("b is: {0}", Asc("b")) End Sub End ModuleInternally, the a and b characters are numbers. So when we compare two characters, we compare their stored numbers. The built-in
Asc
function
returns the ASCII value of a single character.
True a is: 97 b is: 98In fact, we compare two numbers. 97 with 98.
Print("ab" > "aa") ' Prints TrueSay we have a string with more characters. If the first characters are equal, we compare the next ones. In our case, the b character at the second position has a greater value than the a character. That is why "ab" string is greater than "aa" string. Comparing strings in such a way does not make much sense, of course. But it is technically possible.
Finally, we will mention the
Is
operator.
The operator checks if two object references refer to the same object.
It does not perform value comparisons.
Option Strict On Module Example Sub Main() Dim o1 As Object = New Object Dim o2 As Object = New Object Dim o3 As Object o3 = o2 Print(o1 Is o2) Print(o3 Is o2) End Sub End ModuleWe create three objects and compare them with the
Is
operator.
Dim o1 As Object = New Object Dim o2 As Object = New ObjectWe declare and initialize two Object instances. The Object class is a base class for all classes in the .NET framework. We will describe it later in more detail.
Dim o3 As ObjectThe third variable is only declared.
o3 = o2The o3 now refers to the o2 object. They are two references to the same object.
Console.WriteLine(o1 Is o2) Console.WriteLine(o3 Is o2)In the first case, we get False. o1 and o2 are two different object. In the second case, we get True. o3 and o2 refer to the same object.
Bitwise operators
Decimal numbers are natural to humans. Binary numbers are native to computers. Binary, octal, decimal or hexadecimal symbols are only notations of the same number. Bitwise operators work with bits of a binary number. Bitwise operators are seldom used in higher level languages like Visual Basic.Symbol | Meaning |
---|---|
Not | bitwise negation |
Xor | bitwise exclusive or |
And | bitwise and |
Or | bitwise or |
Print(Not 7) ' Prints -8 Print(Not -8) ' Prints 7The operator reverts all bits of a number 7. One of the bits also determines, whether the number is negative or not. If we negate all the bits one more time, we get number 7 again.
The bitwise and operator performs bit-by-bit comparison between two numbers. The result for a bit position is 1 only if both corresponding bits in the operands are 1.
00110 And 00011 = 00010The first number is a binary notation of 6. The second is 3. The result is 2.
Print(6 And 3) ' Prints 2 Print(3 And 6) ' Prints 2The bitwise or operator performs bit-by-bit comparison between two numbers. The result for a bit position is 1 if either of the corresponding bits in the operands is 1.
00110 Or 00011 = 00111The result is
00110
or decimal 7.
Print(6 Or 3) ' Prints 7 Print(3 Or 6) ' Prints 7The bitwise exclusive or operator performs bit-by-bit comparison between two numbers. The result for a bit position is 1 if one or the other (but not both) of the corresponding bits in the operands is 1.
00110 Xor 00011 = 00101The result is
00101
or decimal 5.
v(6 Xor 3) ' Prints 5
Compound assignment operators
The compound assignment operators consist of two operators. They are shorthand operators.Option Strict On Module Example Dim a As Integer Sub Main a = 1 a = a + 1 Print(a) ' Prints 2 a += 1 Print(a) ' Prints 3 End Sub End ModuleThe += compound operator is one of these shorthand operators. They are less readable than the full expressions but experienced programmers often use them.
Other compound operators are:
-= *= \= /= &= ^=
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