Intro and Basic Syntax

Introduction

Visual Basic is a highly popular language in the commercial world because it allows for the rapid development of Windows based programs. VB is particularly strong at creating front ends for databases. This can be done in amazing time through the use of wizards. This page does not cover all aspects of VB, it does not show how to do the basics like layout a form, neither does it cover all the built in functions, as there is already plenty of help provided for these, and a lot of it is self-evident.

A more limited version of Visual Basic is also included in several other Microsoft Applications such as MS Access. Most of the information here applies to that version.

Data Types:

1. Numeric

Byte	Store integer values in the range of 0 - 255
Integer	Store integer values in the range of (-32,768) - (+ 32,767)
Long	Store integer values in the range of (- 2,147,483,468) - (+ 2,147,483,468)
Single	Store floating point value in the range of (-3.4x10-38) - (+ 3.4x1038)
Double	Store large floating value which exceeding the single data type value
Currency	store monetary values. It supports 4 digits to the right of decimal point and 15 digits to the left

2. String

Use to store alphanumeric values. A variable length string can store approximately 4 billion characters

3. Date

Use to store date and time values. A variable declared as date type can store both date and time values and it can store date values 01/01/0100 up to 12/31/9999

4. Boolean

Boolean data types hold either a true or false value. These are not stored as numeric values and cannot be used as such. Values are internally stored as -1 (True) and 0 (False) and any non-zero value is considered as true.

Operators in Visual Basic:

Arithmetical Operators

Operators	Description	Example	Result
+	Add	5+5	10
-	Substract	10-5	5
/	Divide	25/5	5
\	Integer Division	20\3	6
*	Multiply	5*4	20
^	Exponent (power of)	3^3	27
Mod	Remainder of division	20 Mod 6	2
&	String concatenation	"An"&" "&"Apple"	"An Apple"

Relational Operators

Operators	Description	Example	Result
>	Greater than	10>8	True
<	Less than	10<8	False
>=	Greater than or equal to	20>=10	True
<=	Less than or equal to	10<=20	True
<>	Not Equal to	5<>4	True
=	Equal to	5=7	False

Logical Operators

Operators	Description
OR	Operation will be true if either of the operands is true
AND	Operation will be true only if both the operands are true

Array Functions:
Arrays in Visual Basic are very useful things to store a collection of variables or store records. Visual Basic allows any variable type to become an array.

Array([item], [nthitem])
Turns a list of arguments into an array

Example:
Dim a() as String
a() = Array("5","10","15","20")
MsgBox("My Number Is: " & a(3))
' A message box will popup with the text "My Number Is: 20"

IsArray([expr])
Returns a Boolean value that indicates if a specified variable is an array.

Example:
' Create a 3 element array
Dim a(3) as String
a(0) = "Blue"
a(1) = "Green"
a(2) = "Yellow"
IsArray(a)
' True
' Declare a single variable
Dim b as String
b = "Orange"
IsArray(b)
' False

Join(array, [delimiter])
Joins the array elements using the specified delimiter character(s)

Example:
' Declare variables.
Dim days() as String
Dim a as String
days() = Array("Sun","Mon","Tue","Wed","Thu","Fri","Sat")
' The default delimiter for Join() is a space " ".
a = Join(days())
' a="Sun Mon Tue Wed Thu Fri Sat"
a = Join(days(), ",")
' a="Sun,Mon,Tue,Wed,Thu,Fri,Sat"
a = Join(days(), "##")
' a="Sun##Mon##Tue##Wed##Thu##Fri##Sat"

Split(string, [delimiter], [count], [compare])
Split a string into an array that contains the specified number of substrings. When count is ommited, splits into as many substrings as possible.

Example:
' Declare variables.
Dim days() as String
Dim a as String
a="Sun,Mon,Tue,Wed,Thu,Fri,Sat"
days() = Split(a, ",")
MsgBox(days(3))
' Wed

LBound(array)
UBound(array)
Returns the smallest subscript (or largest for UBound) for the specified array

These functions are very useful when you don't know the size of an array.

Example:
Dim days() as String
Dim a as String
days() = Array("Sun","Mon","Tue","Wed","Thu","Fri","Sat")
a = LBound(days())
' a=0
a = UBound(days())
' a=6 

Mathematical Operators:

Example1:

Dim a As Double, b As Double, c As Double
    a = 12: b = 5
    c = a \ b
msgbox(c)    

Print c
End Sub

Output:

2

Example2:

Dim a as Integer

Dim b as Integer

Dim c as Integer

a=1

b= 2

c = a + b

msgbox(c)

End Sub

Output:

3

IF and IF Else Condition:

Example1:

Dim num1 As Integer
num1 = 30
If num1 > 0 Then
msgbox("The number is positive")
End If

Output:
The number is positive.

Example2:
To print the largest number.

Dim num1 As Integer, num2 As Integer
num1 = 30
num2 = 50
If num1 > num2 Then
msgbox( num1)
Else
msgbox( num2)
End If

Output:
50

Nested IF Else:

Example:

a = Val(InputBox("Enter a no."))
If a > 0 Then
Print "Positive"
ElseIf a < 0 Then
Print "Negative"
Else
Print "Zero"
End If

Input and Output Operation:

Example: (TextBox)

Private Sub Command1_Click()
Dim a As Integer
a = Val(Text1.Text)
a = a + 1
Text2.Text = a
End Sub

Example: (Input Box)

Private Sub cmdTakeInput_Click()
Dim n As Integer
n = InputBox("Enter the value of n : ")
Print n
End Sub

Switch Statement:

Example:

Dim num As Integer
num = Val(Text1.Text)
Select Case num
Case 0
Print "You have entered zero"
Case 1
Print "You have entered one"
Case 2
Print "You have entered two"
Case Else
Print "The number you entered is greater than 2"
End Select

Do While Loop:

Example:
To print from 0 to 9.

Dim num As Integer
num = 0
Do While num < 10
Print num
num = num + 1
Loop

Do Loop While:

Example:
To print from 0 to 10.

Dim num As Integer
num = 0
Do
Print num
num = num + 1
Loop While num <= 10

Do Loop Until:

Example:

'x is incremented until x becomes greater than 10

Dim x As Integer
x = 0
Do
x = x + 1
Loop Until x > 10
MsgBox x

For Next Loop:

Example:

Dim i As Integer

For i = 0 To 10
Print i
Next i

Output:

To print 0 to 10.

Example2:

Dim i As Integer
For i = 0 To 6 Step 2
Print i
Next i

Every time, the value of i is incremented by 2.

Output:

0
2
4
6