Introduction to Computing Dr. Nadeem A Khan

Lecture 10

Sub Text1_KeyPress(KeyAscii as Integer) statements statements End Sub ► Text1_KeyPress event will occur when Text1 has the focus and a key is pressed Text1 has the focus and a key is pressed The Keypress Event Procedure

Sub Text1_KeyPress(KeyAscii as Integer) statements 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 The Keypress Event Procedure (Contd.)

What will happen in these cases? Sub Text1_KeyPress(KeyAscii as Integer) Let KeyAscii =65 Let KeyAscii =65 End Sub Sub Text1_KeyPress(KeyAscii as Integer) Let KeyAscii =0 Let KeyAscii =0 End Sub The Keypress Event Procedure (Contd.)

► Already known:  String  Single  Integer Data Types

► 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) (declares a string of a variable length) 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.) Data Types (Contd.)

► 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 Data Types

► Fixed-Length Strings Usage:Result: Hello(Complete string) H…. (H followed 4 spaces) Hello(First 5 characters only) => The length is fix Data Types

► Integers Storage: 2 bytes Range: -32,768 to 32,767 Declaration: Dim intExample As Integer (declares intExample as an Integer variable) (declares intExample as an Integer variable) Data Types (Contd.)

► Integers Usage:Example Dim count As Integer Let count= 6 Picture1.Print count Let count= count+1 Picture1.Print count Let count= 6/5 Picture1.Print count Let count= * 2 Picture1.Print count Data Types

► Integer Usage:Result67 1 (rounding to lower value) 5(rounding to higher value) => takes only whole number values => takes only whole number values Data Types

► 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) (declares lntExample as a long variable) Data Types (Contd.)

► Long (Integer) Usage: Same as Integer Type except the range is much larger much larger Data Types (Contd.)

► Byte Storage: 1 byte Range: 0 to 255 Declaration: Dim bytExample As Byte (declares bytExample as a Byte type variable) (declares bytExample as a Byte type variable) Data Types (Contd.)

► Byte Usage: Same as Integer Type except the range is positive and much smaller positive and much smaller Data Types (Contd.)

► Boolean Storage: 2 bytes Range: TRUE(1) or FALSE(0) Declaration: Dim blnState As Boolean (declares a Boolean type variable blnState) 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= -8*7+5.2 Let blnExample= -8*7+5.2 Picture1.Print blnExample Data Types (Contd.)

► Boolean Usage:Example FALSE FALSE TRUE TRUE =>Values other than 0 are TRUE =>Values other than 0 are TRUE Data Types (Contd.)

► Single (Precision Floating-Point) Storage: 4 bytes Range: -3.4…E38 to -1.4…E-45 (negative) 1.4…E-45 to 3.4…E38 (positive) Declaration: Dim sngAverage As Single (declares a Single type variable sngAverage) Data Types (Contd.)

► Double (Precision Floating-Point) Storage: 8 bytes Range: -1.7…E308 to -4.9…E-324 (negative) 4.9…E-324 to 1.7…E308 (positive) 4.9…E-324 to 1.7…E308 (positive)Declaration: Dim dblAverage As Double (declares a Double type variable dblAverage) 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 Data Types (Contd.)

► Double Usage:Result (Single precision) (Double precision) => Value of 1/3 represented more accurately by double than by single by double than by single Data Types (Contd.)

► Double Usage:Example Dim sngValue As Single, dblValue As Double Let sngValue= 1/3 Let sngValue= sngValue * Picture1.Print sngValue Let dblValue= 1/3 Let dblValue= dblValue * Picture1.Print dblValue Data Types (Contd.)

► Double Usage:Result (Single precision; rounding error) (Double precision) => - The decimal point is floating; - Eventually both will be subjected to rounding errors value increases to large values value increases to large values - Still Double will remain more precise than Single Data Types (Contd.)

► Currency Storage: 8 bytes Range: -922,337,203,685, to 922,337,203,685, ,337,203,685, Declaration: Dim curRevenue As Currency (declares a Currency type variable curRevenue) Data Types (Contd.)

► Currency Usage:Example Dim curValue As Currency Let curValue= 1/3 Picture1.Print curValue Let curValue= 100*1/3 Picture1.Print curValue Data Types (Contd.)

► Currency Usage:Result =>- The decimal point is NOT floating; - Could be used for currency and scientific research - No rounding problems for high values Data Types (Contd.)

► Even more data types  Date Variable: for date and time  Object Variable  Variant Variable  ………. Read the book for more info. Data Types (Contd.)

Not only +,-,*,^ But also: But also: \ opeartor e.g: 5.1\2.04= 2 \ opeartor e.g: 5.1\2.04= 2 MOD operator e.g: 15.2 MOD 6=3 MOD operator e.g: 15.2 MOD 6=3 More on Operators

More on Operators (Contd.) ► Operator Precedence 1. ^ 2.- operator (indicating a negative value) 3. * and / operator 4. \ operator 5. MOD operator 6. + and - operator

Assignment 3 ► Assignment 3 has been posted to the CS101 Website. ► The Deadline is on 6:59 p.m. Wednesday Sept. 25.

Reading for today ► Scott Warner:  Chapter 2: Section 2.3(p60-p66)  Chpater5: Section 5.1