Introduction to Introduction to ComputingComputing

Dr. Nadeem A KhanDr. Nadeem A Khan

Lecture 24Lecture 24

► The general format with step of 1:The general format with step of 1:

For i = m To nFor i = m To nStatementsStatementsNext iNext i

For…Next Loops For…Next Loops

► Convert to For.. Next LoopConvert to For.. Next Loop

Sub Command1_Click ( )Sub Command1_Click ( )Dim num As IntegerDim num As IntegerLet num=1Let num=1Do While num<=10Do While num<=10

Picture1.Print num;Picture1.Print num;Let num=num+1Let num=num+1

LoopLoopEnd Sub End Sub

For Next Loops For Next Loops

► Example with For.. Next LoopExample with For.. Next Loop

Sub Command1_Click ( )Sub Command1_Click ( )Dim num As IntegerDim num As IntegerFor num=1 To 10For num=1 To 10

Picture1.Print num;Picture1.Print num;Next numNext numEnd Sub End Sub

For Next Loops For Next Loops

►The result:The result:

1 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 10

For Next Loops For Next Loops

► The general format with steps:The general format with steps:

For i = m To n Step sFor i = m To n Step sStatementsStatementsNext iNext i

=> Each time increment: i = i + s; => Each time increment: i = i + s; m, n, s could be numeric m, n, s could be numeric

expressions expressions

For…Next Loops For…Next Loops

► Example with For.. Next Loop with Example with For.. Next Loop with stepssteps

Sub Command1_Click ( )Sub Command1_Click ( )Dim num As IntegerDim num As IntegerFor num= 1 To 10 Step 2For num= 1 To 10 Step 2

Picture1.Print num;Picture1.Print num;Next numNext numEnd Sub End Sub

The output?The output?

For Next Loops For Next Loops

►The result:The result:

1 3 5 7 91 3 5 7 9

For Next Loops For Next Loops

► Rewrite the following program using Rewrite the following program using nested For.. Next Loopnested For.. Next Loop

Nested Loops: For…Next Nested Loops: For…Next

Sub Command1_Click ( )Sub Command1_Click ( )Dim num As Integer, counter As IntegerDim num As Integer, counter As IntegerLet counter=1Let counter=1

Do While counter<=4Do While counter<=4 Let num=1Let num=1

Do While num<=10Do While num<=10Picture1.Print num;Picture1.Print num;Let num=num+1Let num=num+1

LoopLoopLet counter=counter+1Let counter=counter+1Picture1.PrintPicture1.PrintLoopLoopEnd Sub End Sub

Nested Loops: For…Next Nested Loops: For…Next

Sub Command1_Click ( )Sub Command1_Click ( )Dim num As Integer, counter As Dim num As Integer, counter As

IntegerIntegerFor counter = 1 To 4 For counter = 1 To 4

For num =1 To 10For num =1 To 10Picture1.Print num;Picture1.Print num;

Next numNext numPicture1.Print Picture1.Print

Next counterNext counterEnd Sub End Sub

Nested Loops: For…Next Nested Loops: For…Next

►The result:The result:

1 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 101 2 3 4 5 6 7 8 9 10

Nested Loops Nested Loops

► Reverses the input stringReverses the input string

Sub Command1_Click ( )Sub Command1_Click ( )Picture1.ClsPicture1.ClsPicture1.Print Reverse$((Text1.Text))Picture1.Print Reverse$((Text1.Text))End Sub End Sub

For Next Loops For Next Loops

Function Reverse$ (info As String)Function Reverse$ (info As String)Dim m As Integer, j As Integer, temp As Dim m As Integer, j As Integer, temp As

StringStringLet temp = “”Let temp = “”For j = Len(info) To 1 Step -1For j = Len(info) To 1 Step -1

Let temp = temp + Mid$(info, j, 1)Let temp = temp + Mid$(info, j, 1)NextNextReverse$ = tempReverse$ = tempEnd FunctionEnd Function

For Next Loops For Next Loops

►Exit For: Works similar as Exit DoExit For: Works similar as Exit Do

Exit For Exit For

Note:Note:

►Read: Schneider Chapter 6, Warner Read: Schneider Chapter 6, Warner Chapter 6 Chapter 6

►Read comments and do practice Read comments and do practice problemsproblems

of these sectionsof these sections►Attempt some questions of ExercisesAttempt some questions of Exercises

Chapter 7:Chapter 7:Array Variables (Arrays) Array Variables (Arrays)

► Array:Array:

A list of values can be assignedA list of values can be assigned

Collection of variables of the Collection of variables of the same typesame type

Array Variables (Arrays) Array Variables (Arrays)

► Array Declaration:Array Declaration:

Dim Dim arrayName arrayName (1 to n) As (1 to n) As varTypevarType

e.g:e.g:

Dim names(1 To 3) as StringsDim names(1 To 3) as Strings

Dim scores(1 To 10) as SingleDim scores(1 To 10) as Single

Array Variables (Arrays) Array Variables (Arrays)

►Value assignment: Value assignment:

Dim names(1 To 3) as StringsDim names(1 To 3) as Strings

Let names(1)=“Aslam”Let names(1)=“Aslam”Let names(2)=“Khalid”Let names(2)=“Khalid”Let names(3)=“Akbar”Let names(3)=“Akbar”Picture1.Print names(3), Picture1.Print names(3),

names(2),names(1)names(2),names(1)

Array Variables (Arrays) Array Variables (Arrays)

►What is what? What is what?

Dim scores(1 To 3) as SingleDim scores(1 To 3) as Single

scores( ): scores( ): name of the arrayname of the arrayscores(1): scores(1): first elementfirst elementscores(2): scores(2): second elementsecond elementscores(3): scores(3): third elementthird element1, 2, 3: 1, 2, 3: subscriptssubscripts

Array Variables (Arrays) Array Variables (Arrays)

►What are the What are the rangesranges or or dimensionsdimensions? ?

Dim scores(1 To 3) as SingleDim scores(1 To 3) as Single

Dim names(1 To 10) as String Dim names(1 To 10) as String

Array Variables (Arrays) Array Variables (Arrays)

End End