Visual Basic Data Types - ZetCode

Contents Previous NextVisual 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.vbOption 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 1. 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.vbOption 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.vbOption 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.vbOption 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.vbOption 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.vbOption 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.vbOption 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.vbOption 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.vbEnum 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.vbOption 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.vbOption 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.vbOption 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.vbOption 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.vbRem 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.

Function	Converts to
CBool	Boolean
CByte	Byte
CChar	Unicode character
CDate	Date
CDb1	Double
CDec	Decimal
Clnt	Integer
CLng	Long
CObj	Object
CShort	Short
CSng	Single
CStr	String

We have several functions to perform explicit conversions.

Program.vbOption 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.

Contents Previous Next