Decision making is very important for the programmer to control the flow of
script or a section of script by using some conditional statements in our
script we can let our program decide whether the given condition is true or
not and accordingly execute further statements.
Following is the general form of a typical decision making structure found in most of the programming languages.
This image above clearly signifies that for our script to perform decision
making we just need to pass the condition to check and then the actions we
need it to perform after evaluation of the statement.
here, it shows that when condition is evaluated and it gets false then, some
part of code gets executed and if the condition evaluated to true then other
part of code is executed.
VBA provides the following types of decision making statements.
- if statement
- if...else statement
- if...elseif...else statement
- nested if statements
- switch statement
1) If Statement :
An if conditional Statement consists of a boolean expression followed
by one or more statements. If the condition is true then statements under if
statements are executed while if the condition is said to be false then
statements after the if Conditionals are executed.
Syntax :
Below is the Syntax of an If conditional statement :
If(boolean_expression) Then Statement 1 ..... ..... Statement n End If!'
Flow Diagram
Example :
Private Sub if_demo() Dim x As Integer Dim y As Integer x = 50 y = 32 If x > y Then MsgBox "X is Greater than Y" End If End Sub
Output :
2) If else Statements
An if else conditional Statement consists of a boolean expression
followed by one or more statements. If the condition is true then statements
under if statements are executed while if the condition is said to be false
then statements under else are executed.
Syntax :
Below is the Syntax of an If Else conditional statement :
If(boolean_expression) Then Statement 1 ..... ..... Statement n Else Statement 1 ..... .... Statement n End If
Flow Diagram
Example :
Program to check greatest number among two numbers.
Private Sub if_demo() Dim x As Integer Dim y As Integer x = 21 y = 32 If x > y Then MsgBox "X is Greater than Y" Else Msgbox "Y is Greater than X" End If End Sub
Output :
3) If Elseif - else Statements
An if elseif-else conditional Statement consists of a boolean
expression under if statement followed by one or more elseif statements and
then followed by a default else statement.
If the condition is true then statements under if are executed while if
the condition is said to be false then statements after the elseif
Conditionals are executed and if all the conditions are evaluated to false
then the default statement is executed.
Note : Else statement is not necessary in any of conditionals while you
can use it if you want to add a default statement to your decision making.
Syntax :
Below is the Syntax of an If ElseIf- Else conditional statement :
If(boolean_expression) Then Statement 1 ..... ..... Statement n ElseIf (boolean_expression) Then Statement 1 ..... .... Statement n ElseIf (boolean_expression) Then Statement 1 ..... .... Statement n Else Statement 1 ..... .... Statement n End If
Flow Diagram
Example :
Program to check greatest number or equality among two numbers.
Private Sub if_demo() Dim x As Integer Dim y As Integer x = 25 y = 25 If x > y Then MsgBox "X is Greater than Y" ElseIf y > x Then Msgbox "Y is Greater than X" Else Msgbox "X and Y are EQUAL" End If End Sub
Output :
4) Nested if Statements
An if or ElseIf statements inside another If or ElseIf statement(s). The inner
if statements are executed based on the outermost if statements. This enables
Script to handle even more complex conditions with ease.
Syntax :
Below is the Syntax of a Nested If conditional statement :
If(boolean_expression) Then Statement 1 ..... ..... Statement n If(boolean_expression) Then Statement 1 ..... ..... Statement n ElseIf (boolean_expression) Then Statement 1 ..... .... Statement n Else Statement 1 ..... .... Statement n End If Else Statement 1 ..... .... Statement n End If
Flow Diagram
Example :
Program to check number is positive or negative , if positive then check whether number is prime,composite or even-odd prime.
Private Sub nested_if() Dim a As Integer a = 32 If a > 0 Then MsgBox "The Number is a POSITIVE Number" If a = 1 Then MsgBox "The Number is Neither Prime NOR Composite" ElseIf a = 2 Then MsgBox "The Number is the Only Even Prime Number" ElseIf a = 3 Then MsgBox "The Number is the Least Odd Prime Number" Else MsgBox "The Number is NOT 0,1,2 or 3" End If ElseIf a < 0 Then MsgBox "The Number is a NEGATIVE Number" Else MsgBox "The Number is ZERO" End If End Sub
Output :
This out is given when first if is encountered and condition is true so,it has gone in nested if that is further statements.
This is the output for nested if condition, all conditions are evaluated and when nothing matched correct it has give the else statement.
5) Switch Statement
When a programmer wants to execute a group of statements depending upon a
value of an Expression, then Switch Case is used. Each value is called a
Case, and the variable is being switched ON based on each case i.e
Statements under any Case are executed if they match correctly.
Case Else statement is executed if the test expression doesn't match any of
the Case specified by the user.
Case Else is an optional statement within Select Case, however, it is a good
programming practice to always have a Case Else statement.
Syntax :
Below is the Syntax of a Switch Case conditional statement :
Select Case expression Case expressionlist1 statement1 statement2 .... .... statement1n Case expressionlist2 statement1 statement2 .... .... Case expressionlistn statement1 statement2 .... .... Case Else elsestatement1 elsestatement2 .... .... End Select
Flow Diagram
Example :
Program to find the type of integer with the help of a function.
Private Sub switch_demo() Dim MyVar As Integer MyVar = 3 Select Case MyVar Case 1 MsgBox "The Number is the Least Composite Number" Case 2 MsgBox "The Number is the only Even Prime Number" Case 3 MsgBox "The Number is the Least Odd Prime Number" Case Else MsgBox "Unknown Number" End Select End Sub
Output :
Post a Comment