Visual Basic data types
last modified October 18, 2023
In this part of the Visual Basic tutorial, we talk about data types.
Computer programs work with data. Tools to work with various data types are essential part of a modern computer language. According to the Wikipedia definition, a data type is a set of values, and the allowable operations on those values.
The two fundamental data types in Visual Basic are value types and reference types. Primitive types (except strings), enumerations, and structures are value types. Classes, strings, standard modules, interfaces, arrays, and delegates are reference types. Every type has a default value.
Reference types are created on the Heap. The lifetime of the reference type is managed by the .NET framework. The default value for reference types is null reference. Assignment to a variable of a reference type creates a copy of the reference rather than a copy of the referenced value.
Value types are created on the stack. The lifetime is determined by the lifetime of the variable. Assignment to a variable of a value type creates a copy of the value being assigned. Value types have different default values. For example, boolean default value is False, decimal 0, string an empty string “”.
Boolean values
There is a duality built in our world. There is a Heaven and Earth, water and fire, jing and jang, man and woman, love and hatred. In Visual Basic the Boolean data type is a primitive data type having one of two values: True or False. This is a fundamental data type. Very common in computer programs.
Happy parents are waiting a child to be born. They have chosen a name for both possibilities. If it is going to be a boy, they have chosen John. If it is going to be a girl, they have chosen Jessica.
Program.vb
Option Strict On
Module Example
Dim num As Byte
Dim male As Boolean
Sub Main()
Randomize()
num = CType(Math.Round(Rnd()), Byte)
If num = 0 Then
male = True
Else
male = False
End If
If male = True Then
Console.WriteLine("We use name John")
Else
Console.WriteLine("We use name Jessica")
End If
End Sub
End Module
The program uses a random number generator to simulate our case.
Dim num As Byte
The num variable has a Byte data type. This is important. Byte data types may have integer values 0..255.
Randomize() num = CType(Math.Round(Rnd()), Byte)
These two lines pick up randomly 0 or 1. The Rnd function returns a random value less than 1, but greater than or equal to zero. We use the Round method to round the number. Random values greater than 0.5 are rounded to 1. All other random values are rounded to 0.
The Double data type is converted into Byte using the CType function. So the num variable is assigned 0 or
- The Randomize function initializes a random-number generator with a seed based on the system timer.
If num = 0 Then male = True Else male = False End If
Depending on the num variable, the Boolean male variable is set to True or False.
If male = True Then Console.WriteLine(“We use name John”) Else Console.WriteLine(“We use name Jessica”) End If
If the male variable is set to True, we choose name John. Otherwise, we choose name Jessica. Control structures like If/Else statements work with Boolean values.
Integers
Integers are a subset of the real numbers. They are written without a fraction or a decimal component. Integers fall within a set Z = {…, -2, -1, 0, 1, 2, …} Integers are infinite.
In computer languages, integers are primitive data types. Computers can practically work only with a subset of integer values, because computers have finite capacity. Integers are used to count discrete entities. We can have 3, 4, 6 humans, but we cannot have 3.33 humans. We can have 3.33 kilograms.
VB Alias
.NET Type
Size
Range
SByte
System.SByte
1 byte
-128 to 127
Byte
System.Byte
1 byte
0 to 255
Short
System.Int16
2 bytes
-32,768 to 32,767
UShort
System.UInt16
2 bytes
0 to 65,535
Integer
System.Int32
4 bytes
-2,147,483,648 to 2,147,483,647
UInteger
System.UInt32
4 bytes
0 to 4,294,967,295
Long
System.Int64
8 bytes
-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
ULong
System.UInt64
8 bytes
0 to 18,446,744,073,709,551,615
These integer types may be used according to our needs. No one, (except perhaps for some biblical people), can be older than 120, 130 years. We can then use the Byte type for age variable in our program. This will save some memory.
Program.vb
Option Strict On
Module Example
Sub Main()
Dim a As Byte = 254
Console.WriteLine(a)
a += Cbyte(1)
Console.WriteLine(a)
a += Cbyte(1)
Console.WriteLine(a)
End Sub
End Module
In this example, we try to assign a value beyond the range of a data type. The compiler ends with System.OverflowException: Arithmetic operation resulted in an overflow.
a += Cbyte(1)
The strict option disallows to add integers to a Byte. (The number literals are Integer data types.) Therefore, we use the Cbyte function, which converts the Integer data type to a Byte.
Integers can be specified in four different notations in Visual Basic: decimal, hexadecimal, octal, and binary. Octal values are preceded by &o, hexadecimal by &h, and binary by &B.
Program.vb
Option Strict On
Module Example
Sub Main()
Dim num1 As Integer = 31
Dim num2 As Integer = &o31
Dim num3 As Integer = &h1A
Dim num4 As Integer = &B01001001
Console.WriteLine(num1)
Console.WriteLine(num2)
Console.WriteLine(num3)
Console.WriteLine(num4)
End Sub
End Module
We assign 31 to three variables using three notations. And we print them to the console.
$ dotnet run 31 25 26 73
The default notation is the decimal. The program shows these four numbers in decimal.
If we work with integers, we deal with discrete entities. We would use integers to count apples.
Program.vb
Option Strict On
Module Example
Sub Main()
Rem number of baskets
Dim baskets As Short = 16
Rem number of apples in each basket
Dim applesinbasket As Short = 24
Rem total number of apples
Dim total As Short = baskets * applesinbasket
Console.WriteLine($"There are total of {total} apples")
End Sub
End Module
In our program, we count the total amount of apples. We use the multiplication operation.
Dim total As Short = baskets * applesinbasket
The Short data type is big enough to count our apples.
$ dotnet run There are total of 384 apples
Floating point numbers
Floating point numbers represent real numbers in computing. Real numbers measure continuous quantities, like weight, height, or speed. In Visual Basic we have three important floating point types: Single, Double, and Decimal.
VB Alias
.NET Type
Size
Precision
Range
Single
System.Single
4 bytes
7 digits
1.5 x 10-45 to 3.4 x 1038
Double
System.Double
8 bytes
15-16 digits
5.0 x 10-324 to 1.7 x 10308
Decimal
System.Decimal
16 bytes
28-29 decimal places
1.0 x 10-28 to 7.9 x 1028
The above table gives the characteristics of the floating point types.
We can use various syntax to create floating point values.
Program.vb
Option Strict On
Module Example
Sub Main()
Dim n1 As Single = 1.234
Dim n2 As Single = 1.2e-3
Dim n3 As Single = 1 / 3
Console.WriteLine(n1)
Console.WriteLine(n2)
Console.WriteLine(n3)
End Sub
End Module
We have three ways to create floating point values. The first is the ’normal' way using a decimal point. The second uses scientific notation. And the last one as a result of a numerical operation.
$ dotnet run 1.234 0.0012 0.3333333
Program.vb
Option Strict On
Module Example
Sub Main()
Dim n1 As Single = 1 / 3
Dim n2 As Double = 1 / 3
If n1 = n2 Then
Console.WriteLine("Numbers are equal")
Else
Console.WriteLine("Numbers are not equal")
End If
End Sub
End Module
Single and Double values are stored with different precision. Caution should be exercised when comparing floating point values.
$ dotnet run Numbers are not equal
And the numbers are not equal.
Let’s say a sprinter for 100 m ran 9.87 s. What is his speed in km/h?
Program.vb
Option Strict On
Module Example
Sub Main()
Dim distance As Single
Dim time As Single
Dim speed As Single
Rem 100m is 0.1 km
distance = 0.1
Rem 9.87s is 9.87/60*60 h
time = 9.87 / 3600
speed = distance / time
Console.WriteLine("The average speed of a sprinter is {0} km/h", speed)
End Sub
End Module
In this example, it is necessary to use floating point values.
speed = distance / time
To get the speed, we divide the distance by the time.
$ dotnet run The average speed of a sprinter is 36.47416 km/h
Enumerations
Enumerated type (also called enumeration or enum) is a data type consisting of a set of named values. A variable that has been declared as having an enumerated type can be assigned any of the enumerators as a value. Enumerations make the code more readable.
Program.vb
Option Strict On
Module Example
Enum Days
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
End Enum
Sub Main()
Dim day As Days = Days.Monday
If day = Days.Monday
Console.WriteLine("It is Monday")
End If
Console.WriteLine(day)
End Sub
End Module
In our code example, we create an enumeration for week days.
Program.vb
Enum Days Monday Tuesday Wednesday Thursday Friday Saturday Sunday End Enum
The enumeration is created with a Enum keyword. The Monday, Tuesday … barewords store in fact numbers 0..6.
Dim day As Days = Days.Monday
We have a variable called day, which is of enumerated type Days. It is initialized to Monday.
If day = Days.Monday Console.WriteLine(“It is Monday”) End If
This code is more readable than if comparing a day variable to some number.
Console.WriteLine(day)
This line prints 0 to the console. For a computer, an enum is a number.
We further work with enumerations.
Program.vb
Option Strict On
Module Example
Enum Seasons As Byte
Spring = 1
Summer = 2
Autumn = 3
Winter = 4
End Enum
Sub Main()
Dim s1 As Seasons = Seasons.Spring
Dim s2 As Seasons = Seasons.Autumn
Console.WriteLine(s1)
Console.WriteLine(s2)
End Sub
End Module
Seasons can be easily used as enums. We can specify the underlying type for the enum plus we can give exact values for them.
Enum Seasons As Byte Spring = 1 Summer = 2 Autumn = 3 Winter = 4 End Enum
With the As keyword we specify the underlying type for the enum. We also give each member a specific number.
Console.WriteLine(s1) Console.WriteLine(s2)
These two lines print 1, 3 to the console.
Strings and chars
String is a data type representing textual data in computer programs. A string in Visual Basic is a sequence of Unicode characters. A Char is a single Unicode character. Strings are enclosed by single or double quotes.
Since strings are very important in every programming language, we will dedicate a whole chapter to them. Here we only drop a small example.
Program.vb
Option Strict On
Module Example
Sub Main()
Dim word As String = "ZetCode"
Dim c As Char = CType(word.SubString(0, 1), Char)
Console.WriteLine(c)
End Sub
End Module
The program prints Z character to the terminal.
Dim word As String = “ZetCode”
Here we create a string variable and assign it “ZetCode” value.
Dim c As Char = CType(word.SubString(0, 1), Char)
The SubString method is used to return a substring from a string. The method return type is a String. We want to retrieve and assign a single character. This is the reason why we need to convert a String to a Char with the CType function. The character is later printed to the terminal.
Arrays
Array is a complex data type which handles a collection of elements. Each of the elements can be accessed by an index. All the elements of an array must be of the same data type.
We dedicate a whole chapter to arrays, here we show only a small example.
Program.vb
Option Strict On
Module Example
Sub Main()
Dim array(5) As Integer
array(0) = 3
array(1) = 2
array(2) = 1
array(3) = 5
array(4) = 6
For i As Integer = 0 To array.Length-1
Console.WriteLine(i)
Next
End Sub
End Module
In this example, we declare an array, fill it with data and then print the contents of the array to the console.
Dim array(5) As Integer
We declare an integer array, which can store up to 5 integers.
array(0) = 3 array(1) = 2 array(2) = 1 array(3) = 5 array(4) = 6
Here we assign values to the created array.
For i As Integer = 0 To array.Length-1 Console.WriteLine(i) Next
We traverse the array and print the data to the console. The Length property of the array gives us the length of the array in question.
Date
A Date is value type, which contain date values, time values, or date and time values.
Program.vb
Option Strict On
Module Example
Sub Main()
Dim today As Date
today = Now()
System.Console.WriteLine(today)
System.Console.WriteLine(today.ToShortDateString())
System.Console.WriteLine(today.ToShortTimeString())
End Sub
End Module
We show today’s date in three different formats. Date & time, date, and time.
Dim today As Date
We declare a variable of Date datatype.
today = Now()
Returns the current date and time, uses the computer’s system date and time.
System.Console.WriteLine(today)
This line prints the date in full format.
System.Console.WriteLine(today.ToShortDateString()) System.Console.WriteLine(today.ToShortTimeString())
The ToShortDateString returns a short date string format, the ToShortTimeString returns a short time string format.
$ dotnet run 9/3/2022 1:27:35 PM 9/3/2022 1:27 PM
Type casting
We often work with multiple data types at once. Converting one data type to another one is a common job in programming. Type conversion or typecasting refers to changing an entity of one data type into another. There are two types of conversion. Implicit and explicit. Implicit type conversion, also known as coercion, is an automatic type conversion by the compiler.
Program.vb
Rem Option Strict On
Module Example
Sub Main()
Dim val As Byte
val = 0.54
Console.WriteLine(val)
Console.WriteLine(12 + 12.5)
Console.WriteLine("12" + 12)
Console.WriteLine("12" & 12)
End Sub
End Module
In this example, we have an bunch of implicit conversions.
Rem Option Strict On
Some of the implicit conversions are not possible when the Option Strict statement is On.
val = 0.54
A floating point value is assigned to the variable of a Byte data type. It is an integer data type. The value is rounded to 1; some precision is lost. This is a narrowing implicit conversion.
Console.WriteLine(12 + 12.5)
We add two values. One integer and one floating point value. The result is a floating point value. It is a widening implicit conversion.
Console.WriteLine(“12” + 12)
The result is 24. The string is implicitly converted to a number.
Console.WriteLine(“12” & 12)
The result is 1212. An integer is converted to a string and the two strings are added.
Next we show some explicit conversions in Visual Basic.
FunctionConverts to
CBoolBoolean
CByteByte
CCharUnicode character
CDateDate
CDb1Double
CDecDecimal
ClntInteger
CLngLong
CObjObject
CShortShort
CSngSingle
CStrString
We have several functions to perform explicit conversions.
Program.vb
Option Strict On
Module Example
Sub Main()
Console.WriteLine(CByte(0.4))
Console.WriteLine(CByte(0.9))
Console.WriteLine(CShort(12 + 12.5))
Console.WriteLine(Val("1071 Fifth Avenue"))
End Sub
End Module
In the program we perform three types of conversions.
Console.WriteLine(CByte(0.4)) Console.WriteLine(CByte(0.9))
These two lines perform a narrowing explicit conversion. The first number is rounded to 0, the second to 1.
Console.WriteLine(Val(“1071 Fifth Avenue”))
The Val function returns the numbers contained in a string. In our case 1071.
$ dotnet run 0 1 24 1071
In this part of the Visual Basic tutorial, we covered data types and their conversions.
