Introduction to Computing

1
Introduction to Computing

• Dr. Nadeem A Khan

2
Lecture 7
3
More on Print method

• Using commas Example
• Picture1.Print North, to, the, future
• Picture1.Print No, 6,

4
More on Print method (Contd.)

• Using commas Result
• North to the future
• No 6 (6 displayed 1 pos. further in
  zone)

5
More on Print method

• Using commas Rules
• Line of a Picture Box divided in zones
• A Zone 14 positions
• Print Items displayed in consecutive zones

6
More on Print method

• Using the Tab function Example
• Picture1.Print HelloTab(10) World
  Tab(20)!
• Picture1.Print NoTab(5)5

7
More on Print method (Contd.)

• Using the Tab function Result
• Hello World ! (World at 10th position)
• (! at
  20th position)
• No 5 (5 at 6th position)

8
More on Print method

• Using the Tab functions Rules
• Tab(n) (where n is a positive integer)
• gtFollowing Item (if possible) displayed
  beginning at the nth position of the line

9
More on Print method

• Using the Spc function Example
• Picture1.Print HelloSpc(3) World
• Picture1.Print NoSpc(3)5

10
More on Print method (Contd.)

• Using the Spc function Result
• Hello World (World after 3 spaces)
• No 5 (5 after 4 spaces)

11
More on Print method

• Using the Spc functions Rules
• Spc(n) (where n is a positive integer)
• gtFollowing Item printed after n spaces

12
More on Print method

• Output to the Printer
• Printer.Print expr
• gtsends expression expr to the printer
• gtworks the same way as Picture1.Print

13
More on Print method (Contd.)

• Output to the Printer
• Let Printer.FontName Script
• Let Printer.FontBold True
• Let Printer.FontSize 12
• gt set properties

14
Decisions
15
Decision StructureFlowchart
Is Condition True
Process Step (s) 2
Process Step (s) 1
16
IF BLOCKS

• IF condition Then
• action1
• Else
• action 2
• End If

17
IF BLOCK (Contd.)

• Complete the program Identifies and displays the
  larger value and its variable (assume unequal
  values)
• Sub Command1_Click
• Dim a As Single, b As Single, largerVal As
  Single
• Let a4
• Let b5
• .
• .
• .
• Picture1. Print Its value islargerVal
• End Sub

18
IF BLOCK (Contd.)
Sub Command1_Click Dim a As Single, b As Single,
largerVal As Single Let a4 Let b5 If agtb
Then Picture1.Print a has the larger
value largerVala Else Picture1.Print b
has the larger value largerValb End
If Picture1. Print Its value islargerVal
End Sub
19
IF BLOCK (Contd.)
Result b has the larger value Its value is
5
20
IF BLOCK (Contd.)
What the following program will do?
21
IF BLOCK (Contd.)
Sub Command1_Click Dim a As Single, b As Single,
largerVal As Single Let a4 Let b4 If (agtb)
Or (ab) Then Picture1.Print a has the larger
value largerVala Else Picture1.Print b
has the larger value largerValb End
If Picture1. Print Its value islargerVal
End Sub
22
IF BLOCK (Contd.)
Result a has the larger value Its value is
4
23
IF BLOCK EXTENDED

• IF condition 1 Then
• action1
• ElseIf condition 2 Then
• action 2
• ElseIf condition 3 Then
• action 3
• End If

24
IF BLOCK EXTENDED(Contd.)
What the following program will do?
25
IF BLOCK EXTENDED(Contd.)
Sub Command1_Click Dim a As Single, b As
Single Let a4 Let b5 If (agtb)
Then Picture1.Print a has the larger
value ElseIf (altb) Then Picture1.Print b has
the larger value Else Picture1.Print a and
b have same value End If End Sub
26
IF BLOCK EXTENDED (Contd.)
Result b has the larger value
27
Conditions
28
Conditions Examples

• Expression True/False
• 2 lt 5 ?
• -5 gt -2.5 ?
• 1 lt 1 ?
• 1 1 ?
• 3.5 lt 3.5 ?
• -9 gt -35 ?
• -2 ltgt -3 ?

29
Conditions Examples (Contd.)

• Expression True/False
• 2 lt 5 True
• -5 gt -2.5 False
• 1 lt 1 False
• 1 1 True
• 3.5 lt 3.5 True
• -9 gt -35 True
• -2 ltgt -3 True

30
Conditions Examples (Contd.)

• Expression True/False
• cat lt dog ?
• cart lt cat ?
• cat lt catalog ?
• 9W lt bat ?
• Dog lt cat ?
• Sales-99 lt Sales-retail ?

31
Conditions Examples (Contd.)

• For strings use the ANSI (or ASCI) table
• Characters ANSI(ASCI) Value
• Digits (0-9) 48-57
• Upper Case (A-Z) 65-90
• Lower Case (a-z) 97-122
• Compare two strings character by character

32
Conditions Examples (Contd.)

• Expression True/False
• cat lt dog True
• cart lt cat True
• cat lt catalog True
• 9W lt bat True
• Dog lt cat True
• Sales-99 lt Sales-retail True

33
Conditions Examples (Contd.)

• Assume a 4 b 3 chello dbye
• Expression True/False
• (a b) lt 2a ?
• (Len(c) - b) (a/2) ?
• c lt good d ?

34
Conditions Examples (Contd.)

• Assume a 4 b 3 chello dbye
• Expression True/False
• (a b) lt 2a True
• (Len(c) - b) (a/2) True
• c lt good d False

35
Conditions (Contd.)

• Condition is an expression involving relational
  operators it is either True or False
• Relational operators
• ltgtltgtltgt

36
Conditions (Contd.)

• Complex Conditions Conditions joined by Logical
  Operators
• cond1 And cond2
• cond1 Or cond2
• Not cond1

37
Conditions Examples (Contd.)

• Assume n 4 answY
• Expression True/False
• (2ltn)And(nlt6) ?
• Not(nlt6) ?
• (answY) Or (answy) ?

38
Conditions Examples (Contd.)

• Assume n 4 answY
• Expression True/False
• (2ltn)And(nlt6) True
• Not(nlt6) False
• (answY) Or (answy) True

39
Conditions (Contd.)

• Operator hierarchy
• In decreasing order of priority
• Arithemetic
• Relational
• Logical
• Logical operator hierarchy
• In decreasing order of priority
• Not
• And
• Or

40
Conditions (Contd.)
gt - Tie Left most operator is
first - Use parantheses
41
Reading Data from File

• Open filespec For Input As n
• Opens a file for reading and assigns the
  reference number n
• Input n, var
• Next available item is read from the file and
  assigned to variable var
• Close n
• Closes the file

42
Reading Data from File (Contd.)

• DATA.TXT file has two lines
• September
• 26
• gt items separated by commas or line-breaks
• data item of same type as the data to be
• assigned to the corresponding variable

43
Reading Data from File (Contd.)

• Example
• Sub Command1_Click()
• Dim month As String, date As Single
• Picture1.Cls
• Open DATA.TXT For Input As 1
• Input 1, month
• Input 1, date
• Picture1.Print Today is month date
• Close 1
• End Sub

44
Reading Data from File (Contd.)

• The result
• Today is September 26

45
Writing Data from File

• Open filespec For Output As n
• Opens a file for writing and assigns the
  reference number n
• Write n, expression list separated by commas
• Expression list with each expression separated by
  comma is written on the next line in the file
• Close n
• Closes the file

46
Writing Data from File (Contd.)

• Example
• Sub Command1_Click()
• Dim name1 As String, num As Single
• name1Ahmad
• num123.4
• Open DATA.TXT For Output As 1
• Write 1, Hello
• Write 1, name1, num
• Write 1, 14139, Hassan name1
• Close 1
• End Sub

47
Writing Data to File (Contd.)

• The result
• Hello
• Ahmad,123.4
• 1946,HassanAhmad

48
The Message Box for Output

• MsgBox message, , Caption
• A Message Box will appear
• displaying the string message
• Caption will appear in the title bar

49
The Input Box for Input

• Let stringVar InputBox(message)
• gtAn InputBox will appear displaying the string
  message Assigns the typed user response to
  stringVar after Enter is pressed or OK is
  clicked

50
Input/Output Example

• Example
• Sub Command1_Click()
• Dim first As String, middle As String, last As
  String
• Open D\Names.txt For Input As 1
• Input 1, first, last
• middle Inputbox(enter your middle name)
• MsgBox first middle last, ,
  The full name
• Close 1
• End Sub

51
Inclusion of Comments

• Rem text
• .. text
• e.g
• Rem Compute weekly pay
• Dim hrs as Single hours worked

52
Loop structure General Format

• Do While condition
• statements
• Loop

53
Flow chart loop structure
No
Is condition true ?
Yes
Process Step(s)
54
Do Loops

• Example 1
• Sub Command1_Click ( )
• Dim num As Integer
• Let num1
• Do While numlt10
• Picture1.Print num
• Let numnum1
• Loop
• End Sub

55
Do Loops

• The result
• 1 2 3 4 5 6 7 8 9 10

56
Do Loops (Contd.)

• Example 2
• Sub Command1_Click ( )
• Dim passWord as String, info As String
• If Ucase(Text1.Text) SECRET.TXT Then
• Let passWord
• Do While passWord ltgt SHAHID
• Let passWord InputBox(Enter passWord)
• Let passWord Ucase(passWord)
• Loop
• End If
• Remaining statements on next slide

57
Do Loops (Contd.)

• Example 2 (Contd.)
• Continues from the previous slide
• Open Text1.Text For Input As 1
• Input 1, info
• Picture1.Print info
• Close 1
• End Sub

58
Do-Loop-Until General Format

• Do
• statements
• Loop Until condition
• Flow chart?

59
Do-Loop-Until General Format

• Modify example 2 to Do-loop-Until Format

60
Do-Loop-Until (Contd.)

• Example 1
• Sub Command1_Click ( )
• Dim passWord as String, info As String
• If Ucase(Text1.Text) SECRET.TXT Then
• Do
• Let passWord InputBox(Enter passWord)
• Let passWord Ucase(passWord)
• Loop Until passWord SHAHID
• End If
• Remaining statements on next slide

61
Do-Loop-Until (Contd.)

• Example 1 (Contd.)
• Continues from the previous slide
• Open Text1.Text For Input As 1
• Input 1, info
• Picture1.Print info
• Close 1
• End Sub

62
Do-Loop Another Example

• When will the following program come to its end?

63
Do-Loop Another Example

• Sub Command1_Click ( )
• Dim num As Single
• num 7
• Do While num ltgt 0
• numnum-2
• Loop
• End Sub