Introduction to Computing

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Introduction to Computing

• Dr. Nadeem A Khan

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Lecture 10
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The Keypress Event Procedure

• Sub Text1_KeyPress(KeyAscii as Integer)
• statements
• End Sub
• Text1_KeyPress event will occur when
• Text1 has the focus and a key is pressed

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The Keypress Event Procedure (Contd.)

• Sub Text1_KeyPress(KeyAscii as Integer)
• statements
• End Sub
• Keyascii
• is a variable (of type Integer)
• gets the ANSI value of the pressed key
• value is used to display the corresponding
  character in the Text1 at the end of this
  procedure

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The Keypress Event Procedure (Contd.)

• What will happen in these cases?
• Sub Text1_KeyPress(KeyAscii as Integer)
• Let KeyAscii 65
• End Sub
• Sub Text1_KeyPress(KeyAscii as Integer)
• Let KeyAscii 0
• End Sub

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Data Types

• Already known
• String
• Single
• Integer

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Data Types (Contd.)

• Strings
• Storage 10 bytes string length
• Range 0 to app. 2 billions chars.
• Declaration
• Dim strVarLen As String
• (declares a string of a variable length)

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Data Types (Contd.)

• Fixed-Length Strings
• Storage Length of string
• Range 1 to app. 65, 400 chars.
• Declaration
• Dim strFixLen As String 2
• (declares a string of a fix size of 2 chars.)

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Data Types

• Fixed-Length Strings
• Usage
• Example
• Dim strText As String 5
• Let strText Hello
• Picture1.Print strText
• Let strText H
• Picture1.Print strText
• Let strText HelloWorld
• Picture1.Print strText

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Data Types

• Fixed-Length Strings
• Usage
• Result
• Hello (Complete string)
• H. (H followed 4 spaces)
• Hello (First 5 characters only)
• gt The length is fix

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Data Types (Contd.)

• Integers
• Storage 2 bytes
• Range -32,768 to 32,767
• Declaration
• Dim intExample As Integer
• (declares intExample as an Integer variable)

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Data Types

• Integers
• Usage
• Example
• Dim count As Integer
• Let count 6
• Picture1.Print count
• Let count count1
• Picture1.Print count
• Let count 6/5
• Picture1.Print count
• Let count 2.33333 2
• Picture1.Print count

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Data Types

• Integer
• Usage
• Result
• 6
• 7
• 1 (rounding to lower value)
• 5 (rounding to higher value)
• gt takes only whole number values

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Data Types (Contd.)

• Long (Integer)
• Storage 4 bytes
• Range -2,147,483,648 to 2,147,483,647
• Declaration
• Dim lngExample As Long
• (declares lntExample as a long variable)

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Data Types (Contd.)

• Long (Integer)
• Usage Same as Integer Type except the range is
• much larger

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Data Types (Contd.)

• Byte
• Storage 1 byte
• Range 0 to 255
• Declaration
• Dim bytExample As Byte
• (declares bytExample as a Byte type variable)

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Data Types (Contd.)

• Byte
• Usage Same as Integer Type except the range is
• positive and much smaller

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Data Types (Contd.)

• Boolean
• Storage 2 bytes
• Range TRUE(1) or FALSE(0)
• Declaration
• Dim blnState As Boolean
• (declares a Boolean type variable blnState)

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Data Types (Contd.)

• Boolean
• Usage
• Example
• Dim blnExample As Boolean
• Let blnExample FALSE
• Picture1.Print blnExample
• Let blnExample 1
• Picture1.Print blnExample
• Let blnExample 6
• Picture1.Print blnExample
• Let blnExample -875.2
• Picture1.Print blnExample

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Data Types (Contd.)

• Boolean
• Usage
• Example
• FALSE
• TRUE
• TRUE
• TRUE
• gtValues other than 0 are TRUE

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Data Types (Contd.)

• Single (Precision Floating-Point)
• Storage 4 bytes
• Range -3.4E38 to -1.4E-45 (negative)
• 1.4E-45 to 3.4E38 (positive)
• Declaration
• Dim sngAverage As Single
• (declares a Single type variable sngAverage)

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Data Types (Contd.)

• Double (Precision Floating-Point)
• Storage 8 bytes
• Range -1.7E308 to -4.9E-324 (negative)
• 4.9E-324 to 1.7E308 (positive)
• Declaration
• Dim dblAverage As Double
• (declares a Double type variable dblAverage)

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Data Types (Contd.)

• Double
• Usage
• Example
• Dim sngValue As Single, dblValue As Double
• Let sngValue 1/3
• Picture1.Print sngValue
• Let dblValue 1/3
• Picture1.Print dblValue

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Data Types (Contd.)

• Double
• Usage
• Result
• 0.3333333 (Single precision)
• 0.333333333333333 (Double precision)
• gt Value of 1/3 represented more accurately
• by double than by single

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Data Types (Contd.)

• Double
• Usage
• Example
• Dim sngValue As Single, dblValue As Double
• Let sngValue 1/3
• Let sngValue sngValue 100000
• Picture1.Print sngValue
• Let dblValue 1/3
• Let dblValue dblValue 100000
• Picture1.Print dblValue

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Data Types (Contd.)

• Double
• Usage
• Result
• 33333.34 (Single precision rounding error)
• 33333.3333333333 (Double precision)
• gt - The decimal point is floating
• - Eventually both will be subjected to rounding
  errors
• value increases to large values
• - Still Double will remain more precise than
  Single

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Data Types (Contd.)

• Currency
• Storage 8 bytes
• Range -922,337,203,685,477.5808 to
• 922,337,203,685,477.5807
• Declaration
• Dim curRevenue As Currency
• (declares a Currency type variable curRevenue)

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Data Types (Contd.)

• Currency
• Usage
• Example
• Dim curValue As Currency
• Let curValue 1/3
• Picture1.Print curValue
• Let curValue 1001/3
• Picture1.Print curValue

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Data Types (Contd.)

• Currency
• Usage
• Result
• 0.3333 33333.3333
• gt - The decimal point is NOT floating
• - Could be used for currency and scientific
  research
• - No rounding problems for high values

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Data Types (Contd.)

• Even more data types
• Date Variable for date and time
• Object Variable
• Variant Variable
• .
• Read the book for more info.

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More on Operators

• Not only ,-,,
• But also
• \ opeartor e.g 5.1\2.04 2
• MOD operator e.g 15.2 MOD 63

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More on Operators (Contd.)

• Operator Precedence
• 1.
• 2.- operator (indicating a negative value)
• 3. and / operator
• 4. \ operator
• 5. MOD operator
• 6. and - operator

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Assignment 3

• Assignment 3 has been posted to the CS101
  Website.
• The Deadline is on 659 p.m. Wednesday Sept. 25.

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Reading for today

• Scott Warner
• Chapter 2 Section 2.3(p60-p66)
• Chpater5 Section 5.1