Chapter 1: Representing Data

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2 Chapter 1: Representing Data Data Variables and Constants When you input data into a computer, the computer stores it in its memory 1- Computer's memory consider as millions of little boxes. 2- Each little box has a number, starting at box number zero. 3- The actual number of boxes in your computer depends upon the size of memory. Each memory location (each box ) can hold a byte, where the byte can store a single character or can store an integer number. If the number you want to store is greater than the maximum value, you have to store it in a number of memory. Visual Basic allow you to set up locations in memory and give each group of locations a name. For example: 1- Quantity is the name of a memory locations that hold the number of books. 2- Unit Price is the name of memory locations that hold the price of a single book. 3- Price is the name of memory locations that hold the price of all the books. Quantity, Unit Price, and Price are variables. Variables: Memory locations that hold data that can be changed during program execution Constants: Memory locations that hold data that can not be changed like sales tax rate or Π ( 3.14 ) Note: We used ' Dim ' just once to declare each variable. Data Types Representing data as sequences of Ones and Zeros. - ٢ -

3 The data type of a variable or constant indicates the type of information that will be stored in the allocated memory space, where the size of the memory space allocated for each type is different. The standard data types : 1- Number of Bytes shows the number of bytes of main memory. 2- Range refers to the largest and smallest values that can be stored in a numeric variable Data Type Number of Bytes Precision Boolean 2 Not Applicable Byte 1 Whole numbers only Char 2 Not Applicable Date 8 Not Applicable Decimal digits Single 4 7 significant digits Double 8 15 significant digits Short 2 5 digits whole numbers only Integer 4 10 digits; Whole numbers only Long 8 19 digits; whole numbers only String Varies Not Applicable Note : Type Integer, Long, and Short can store only( integer values ). Type Decimal, Single, and Double store ( fractional values ). Variable Type Explanation SingQuantity Single Maximum Precision of 7 significant digits is reached DoubQuantity Double Maximum Precision of 15 significant digits is reached DecQuantity, Decimal The whole number is stored because the number is 17 digit where the precision for Decimal is 29 digits. Naming Rules A programmer has to name ( identify ) the variables and constants that will be used in a project according to the following rules : a- Names may consist of letters, digits, and under scores. - ٣ -

4 b- Names must begin with a letter. c- Names cannot contain any spaces or periods. d- Names must not be reserved words.( such as print, Dim, double, and Data ) Note : It is better to use the following Naming Conventions a- Identifiers should be meaningful. For Example to name an identifier the average, just call it average. b- Capitalize each successive word of the name. For Example to name a variable " hours worked ", write the name as " Hours Worked". The Identifiers in VB are not case sensitive. There fore the names hoursworked, Hours worked, and hoursworked refer to the same variable. For Example: The following list shows examples of valid variable names : First Name Ahmed 2000 Population of Egypt Spent Money The following list shows some invalid variable names : Variable Name Cause of Invalidation of Variable Name 2 nd World War Variable name must start with character Spent. Money Variable name contains period Birth Day Variable name contains space Double Variable name is a reserved word Choosing the appropriate data type for a variable The following table contains a set of decision rules, to select the best type for that variable. Nature of value to be stored - ٤ - Appropriate Type Reason Something that is True or False Boolean Most efficient storage Sequence of characters that are not involved in arithmetic String The only choice Money Amount Decimal Can store pound and piaster with no round off error ;

5 fast arithmetic Whole Number <=Number<= ,147,483,648<=Number <=2,147,483,647 Number >2,147,483,647 Short Integer Long Less Memory faster arithmetic than other numeric types Less memory and faster than Log Number with fractional part -(10) 38 <Number<(10) 38 or Seven digits of significance Single Faster arithmetic than Double Number >(10) 38 or more than Seven digits of significance Double Constants Constants provide a way to use words to describe a value that does not change. Visual Basic.NET has two types of constants: Intrinsic constants and Named constants 1- Intrinsic constants Intrinsic Constants are built into. NET framework. Visual Basic provides an easy way to specify a large number of colors. Color.Black Color.Blue Color. Red Variables Declaring a Variable using { Dim Statement } To create a variable 1- You write a variable declaration which begins with the keyword " Dim ". 2- The name of the variable to be declared. 3- The keyword " As ". 4- The data type for the variable finally an optional equal sign and initial value. - Dim Child Weight as Integer. - ٥ -

6 - Dim Population as Integer. - Dim Student Name as String - Dim My Address as String = " 102, Salah Salem, Cairo " Declaring multiple variables using one Dim statement. You can declare multiple variables using a single Dim Statement. For example : Dim Child Weight, Population as Integer Dim UnitPrice as Decimal = 123, My Address as String = " 102, Salah Salem, Cairo " Dim Student Name as String The assignment Statements : To change the value stored in a variable you have to use an assignment statement. Variable Name = Expression Note : You have to create the variable using variable declaration statement before you can use it in an assignment Statement. For Example you can write the following assignment statement in programming Count = Count + 1 The new value of Count is equal to the previous value of count plus 1 but In mathematics this equation is wrong because if we subtract count from both sides we will get a value 1. To execute an assignment statement, the computer does two steps : a. Determines the value of the expression on the right-hand side of the assignment sign by i- Replacing the constant names and variable names by their values. ii- Executing the needed operations. b. Store the value of the expression in the variable whose name is on the left-hand side of the assignment sign. For Example : The following assignment statement : Statement Quantity Unit Price Price Tax rate 4 Bytes 16 Bytes 16 Bytes 16 Bytes Dim Quantity As Integer = Doesn't exist Doesn't exist Doesn't exist Dim Unit Price As Decimal = Doesn't exist Doesn't exist - ٦ -

7 Price = Quantity * Unit Price *5.5= The computer executes this assignment statement as follows : Exercise 1: a- It determines the value of the expression as follows : 1- Replacing Quantity, Unit Price by 100 and 5.5 respectively. As a result of this expression will look as follows : 100* Executing the multiplication. As a result of this the expression value will be equal to 55.0 b- It stores the value of the expression (550.0 ) in Price. 1- We stored the value of 20 into the variable count. 2- The computer replaces variable name count to the right-hand side by its value (20) 3- As a result of this the expression will be equal to The computer will store 21 into the variable on the left-hand side. That means that the new value of count will be 21. Trace the following piece of code Dim X As Short Dim Y As Short Dim Z As Short X = 10 X = 2 * X + 1 Y = X-8 Z = Y / 3 Z = Z + 4 Note that tracing means showing the contents of all variables for every statement. Solution Statement X Y Z Dim X As Short 0 Does not exist Does not exist Dim Y As Short 0 0 Does not exist Dim Z As Short X= X=2*X Y=X Z=Y/ Z=Z ٧ -

8 Note that : 1- The 7 th. Statement is the division of 13 by 4 which Exact result is Because Z is an integer variable, only the value of 3 will be stored in it. 2- The value of 0.25 will be neglected. Important : If you want to store the floating point number 3.25 in Z, you have to change its type into single, Double, or Decimal data type. The Assignment Statements for Strings : You can use the assignment statement to store the result of string manipulations into a string variable just as you store the result of arithmetic calculations in a numeric variable Exercise 2 Trace the following piece of code : Dim First name As String Dim Last Name As String Dim Message As String First Name = " Hany " Last name = " Ahmed" Message = "Welcome " & First Name & " Last name " Solution Statement First name Last name Message Dim First name As String Does not exist Does not exist Dim Last Name As String Does not exist Dim Message As String First name = " Hany " " Hany " Message = " Wlecome" & First Name & & Last Name " Hany " "Ahmed" " Welcome Hany Ahmed " Note: means an empty string, where means a string that contains a number of spaces Arithmetic Operations The following table shows the arithmetic operations that - ٨ -

9 Operator Operation + Addition - Subtraction * Multiplication / Disision \ Integer Division Mod Modulus ( Remainder of division ) ^ Exponentiation Important Note : A- The Integer division and the Modulus ( Remainder of division ) If we divide 48 5 = 9 3 / 5 1- Integer division 48 / 5 = 9 2- Reminder of the division 98 Mod 5 = 3 B- The Exponentiation Exponentiation operator ( ^ ) raises a number to the power specified the returned ( Produced ) value is type Double For example, if x = 5, then y = x ^ 2, 25.0 where has to be of type Double. Exercise : Create a project that contains a single form which " Name " property is " Form 1 ". " Form 1. Text" must be set to " Math ". The form hosts two text Boxes txtfirst, and txt Second The results of addition, subtraction, multiplication, division, integer division, modulus, and exponentiation of the contents of the two text Boxes' are Solution : 1- Plan the project : The first step in planning is to design the user interface. 2- Creating your VB project : ( Choose New Project from the Visual Studio main menu, or double click " Create Project " in the " Recent Projects " pane ) 3- In the Project types pane choose windows and in Templates pane double click windows application. - ٩ -

10 4- Type the name you want of your project " Math ". 5- Click OK. 6- Set up the form (Resize the form in the document window : Drag the resize Handles to make the suitable size ). 7- Place controls on the form " Form 1 " After placing the two text Boxes, the 16 label, and the button, we have to change the properties needed for each control. Name Property Setting Txt Box1, txt Box 2 Text Text Align Font Font Style Font Size Center Microsoft Sans Serif Bold 10 IbiLable 1 Text & First IBI Label 2 Text & Second IBiLabel 1 thhrough IBILabel 7 Text Fixed 3 D Border Stype Ibi Add, Ibi Sub, IbI Mul, Ibi Div, Ibi Int Div, Ibi Mod, IbI Exp Text +, -, *, /, \ Mod, ^ Button 1 Text Calculate 8- Align the controls on the Form : 9- Double click on Button 1. (This will open up the Code window and also create the first and last statements of the Click Event Handler) - ١٠ -

11 Public class Form l Private, sub Button 1 click ( By Va 1 sender As system. Object, By Vale As system. Event Args ) Handless Button. click 'Declare the local variables 1 Dim First, seond, ad, subtract, Mul, Div, Div2 As Decimal 2 Dim Modulus As Integer 3 Dim Expon As Double 'Convert the text strings to decimal 4 First = Decimal, Parse (Me txt first. text ) 5 Second = Decimal Parse (me txt Second. Text ) 'Calculate the values of local variables 6 ad = first + Second 7 Ibl Add. text = ad. To String ( ) 8 Subtract = first second 9 Ibi Sub. Text = subtract. To String ( ) 10 Mul = first * Second 11 Ibi Mul. txt = Mul. To string 12 Div = First / second 13 IBIDiv. Text = Div. To String ( ) 14 Div 2 = first / second 15 IBI Int Div. Text = Div 2 To String ( ) 16 Modulus = first Mod Second 17 IBI Mod. Text = Modulus. To String ( ) 18 Expon = first ^ second 19 IBI Exp. Text = Expon. To String ( ) 20 End Sub End Class 10- Enter any nonnumeric values. The program will stop and an error message will be displayed. - ١١ -

12 Precedence of Operations The Operations are performed determines the result * 2 The rules of Precedence for evaluation of an expression is performed in the following order from highest to lowest : 1. Operations within parentheses. 2. Exponentiations. 3. Multiplication and division operations 4. Integer division operations. 5. Modulus operations. 6. Addition and subtraction operations Multiple operations at the same level ( such as multiplication and division ) are performed left to right. Exercise : What is the result of evaluation of the following expressions? Assume that x Integer = 2 yinteger = 3 zinteger = 4 Solution : i- x Integer * ( y Integer + 1 ) is replaced by 2 * ( ) the parenthesis is evaluated first giving 2 * 4 then, the multiplication is performed giving 8 the result ii- Y Integer ^ x Integer * x Integer + z Integer * 3 is replaced by 3 2 * * 3 the exponentiation is evaluated first 9 * * 3 the multiplication at the left is performed giving *3 the multiplication at the right is performed giving the addition is performed 30 the result - ١٢ -

13 Questions A) Multiple choice questions : 1. The conversion from a narrower numeric data type to another one which is wider is referred to as a ( n ) implicit conversion. 2. The zero value is represented by in V B. 3. Which of the following declares three Integer and two string variables? Dim N1, N2, N3 As Integer, S1 S 2 As String 4. When a value is placed in a memory location, the value replaces the previous contents of the memory location. 5. When a value is read from a memory location, the value is not affected. 6. The expression to the right of the assignment operator = is evaluated before the assignment occurs. 7. The( \ )operator performs Integer division. 8. Variable declarations begin with the keyword Dim. 9. The To String function converts a numeric value into a string type. 10. Arithmetic expressions are evaluated from highest level of precedence to the lowest level of precedence. B) The code in Figure 1-8 modifies variables num 1, num 2 and num 3. Trace the given code showing the contents of all variables for each step, given that num 1, num 2 and num 3 are equal to 1,2 and 3 respectively. Dim num1, num 2, num 3 As Integer num 3 = num 1 + num 2 + num 3 num 3 = num 3 Mod 3 num 2 = num num 1 = 4 num 2 = num 1 3 num 1 = num 1 + num 1 num 2 = num1 + num 3 num 2 = 5 * num 2 \ num1-١٣ -

14 Statement Num 1 num 2 Num 3 Dim Num 1, Num 2, Num 3 as Integer Num 3 + Num 1 + Num 2 + Num Num 3 + num 3 Mod Num 2 = num Num 1= Num 2 = Num Num 1= num 1 + num Num 2 = num 2 + num Num 2 = 5 * num 2 / num 1 8 5/8 0,625 zero 0 C) What is wrong with the expression shown in Figure Dim number 1 As Integer Number 1 = ( 4 * 3 ^ 2 ) / ( 10 Mod 3 1 ) Dim number 1 as integer Number 1 = ( 4 * 3 ^ 2 ) / ( 10 Mod 3 1 ) * Brackets First : ( 4 * 9 ) / ( 1 1 ) 36 / 0 = The error is We can't divide any number over Zero. D) Project Create a project that contains a single form which " Name " Property is " Form 1 " which text property is set to " Average ". The form hosts three Text Boxes txt First, txt Second and txt Third. In addition to that the form hosts one button and five labels as shown in Figure 1-10 you have to enter three decimal numbers in the three text boxes. The average of the three numbers has to be displayed in label ١٤ -

15 Chapter 2: Condition and Decisions Using Conditional Expressions A conditional expression is an expression that asks a True-or-False question about a variable, a property, or a piece of data in the program code. For example, the conditional expression Score > 90 Means: is the score more than 90? This expression evaluates to True if the Score is more than 90, otherwise it evaluates to False. Symbol Relation Tested Example Result > Greater than A >B False < Less than A < B True = Equal to A = B False < > Not equal to A< >B True > = Greater than or equal to A > = B False < = Less than or equal to A< = B True If Then Else Statement. A decision made by a computer depends on the result of the question : Is a given condition True or False? If it is True, do one thing ; it is False do something else. This can be seen in the Flow Chart. - ١٥ -

16 The outcome of the condition is evaluated to be True or False - If the outcome is True : the computer executes statement block 1, then skips to the statement following End If. - If the outcome is False : the computer executes statement block 2, then executes the statement following End If. The syntax of the If Then Else statement If condition then Statement block 1 Else Statement block 2 End If For Example Write a program that can calculate the weekly salary of an employee. If his working hours is less than or equal to 40 hours, his salary is 5 L. E. If his working hours is greater than 40 hours, his salary is calculated as follows : i- Five pounds / hour for the first Forty hours. ii- Ten pounds / hour for working hours greater then 40. That means that his salary = 40 * * ( working hours 40 ) - ١٦ -

17 If Hours worked > 40 then Over Time = 10 * ( Hours Worked 40 ) Salary = 40 * 5 + Over Time Else Salary = 5 * Hours Worked End If Msg Box ( " The salary is equal to " & Salary ) - ١٧ -

18 Simple If Then Statement Note : 1. If.. Then statement is a simplified version of the If Then.. Else statement. 2. If.. Then.. Else is useful when the two outcomes execute either action A or action B 3. If..Then statement is useful when the two outcomes execute either action A or no action. The effect of the If. Then statement as follows : The outcome of evaluating the condition can be either True or False. - If the outcome is True : the computer executes statement block 1, then skips to the statement following End If. - If False : The computer skips immediately to the statement following End If. If condition Then End If Statement block 1 For Example If Age > 16 Then Msg Box (" You can get an ID card " ) End If - ١٨ -

19 If Then.. Else statement General Form Note : The conditional expressions are evaluated from the top downward. Compound Conditions Compound conditions can be used to test more than one condition. You can create compound condition by joining more than one condition using logical operators. [ Or, Or Else, And, And Also, Xor ( exclusive Or ), and Note ] Logical operator If condition 1 Then Statement block 1 Else If conditions 2 Then Statement block 2... Else Astatement block2 End if Meaning Example Result or If one condition or both conditions are True, the compound condition is True. firstinteger = 50 Or secondinteger > 200 True Or False True And Both conditions must be True to get the compound condition equal to True. FirstInteger <= 50 And secondinteger < 200 True And False False Note : 2 Items are True and 4 Items one false Important Note First Second Logical Operator Condition Condition And Or T T T T F T F T T F F T F F F F T F Not ( T ) = F Not ( F ) = T - ١٩ -

20 Comparing Strings : We can compare string variables to other string variables, string literals enclosed in quotation marks, or string properties. The ranking of the characters is based on the code used to store characters in the computer. The code called ANSI code ( American National Standards Institute code ) Note : 1- The code of letter A is less than the code of letter Z ( A = 65, B = 66, C = 67 Z = 90 ) 2- The numeric digits ane less than letters. 3- The Start of code is space = 32 When the end of code is Del = 127 For more information see table 2-5 Page 60 For Example : 1- txtperson1.text = "NEHAD", txtperson2.text = " NEHAL " 2-1b1Street1.Text = "SALAH SALEM", Ib1Street2.Text = "SALAH" 3- Ib1 Car 1 text = " Cairo ", Ib 1 Car 2. Text = " Nasr " 4- txtname1.text = "ahmed", txtname2.text = "Ahmed " i. txtperson1.text < txtperson2.text ii Ib1Street1.Text < Ib1Street2.Text iii. Ib1Car1.Text < Ib1Car2.Text iv. txtname1.text < textname2.text Solution : 1. The condition txtperson1.text < txtperson2.text evaluates True because the D in NEHAD is lower ranking than the L in NEHAL. 2. The condition Ib1Street1.Text < IB1Street2.text evaluates False because when one string is shorter than the other, we compare them as if the shorter string was padded with blanks to the right of the string, we are comparing the two strings : "SALAH SALEM" and "SALAH" Which results that "SALAH SALEM" is more than "SALAH " Because S in SALEM is higher rank than the corresponding space in " SALAH " 3. The condition Ib1Car1.Text < Ib1Car2.Text evaluates True because the number 8 is compared to letter N and 8 is lower than N. 4. The condition txtname1.text < txtname2.text evaluates False because the a in Ahmed have a higher ranking than A. - ٢٠ -

21 Using IF Statements with Radio Buttons, Check Boxes, and Group Box Controls Radio Button control Check Box control Group Box control presents the user with a set of options from which to select just one option Radio Button Controls : presents the user with a set of options from which to select any number of options at the same time - ٢١ - allows the developer to group the Radio Buttons and Check Boxes to different groups of items such that the user can choose just one Radio Button from each group Radio Button controls are commonly used to represent program options. Radio Button Properties Property Action Name (rad ) Gets or Sets the name of the control. Appearance Represents whether the radio button looks like a traditional radio button or like a button. Back Color Represents the radio button's background color Checked Represents whether the radio button is checked Enabled Represents whether the user can interact with the radio button Fore Color Height Image Represents the color of the radio button text Represents the radio button height Represents the image that is displayed in the button Text Represents the radio button text Visible Represents whether the radio button is visible Width Represents the radio button's width Users sometimes have to make decisions that require selecting a combination of options from a set of alternatives. A Check Box appears as descriptive text next to a square. The essential difference between Radio Buttons and Check Boxes is that the radio Buttons have the restriction that the user selects only one option, whereas the Check Boxes do not. Check Box Properties Property Action Name ( chk) Gets or Sets the name of the control. Appearance Represents whether the check box looks like a traditional check box or like a button. Back Color Represents the check box background color Checked Represents whether or not the check box is checked or not ( True or False ) Enabled Represents whether the user can interact with the check box. Fore Color Represents the color of the check box text Height Represents the check box height Image Represents the image that is displayed in the button Text Visible Width Represents the check box text Represents whether the check box is visible Represents the check box width

22 The Group Box control Group Box control appears as a rectangle surrounding the controls it groups together. The group's Text property can be used to help identify the group to which the contents relate. Group Box Properties Property Name Enabled Flat Style Visible Action (grp) Gets or Sets the name of the control If the group box is not enabled ( value set to False ), than all the controls it contains also are not enabled Gets or sets the flat style appearance of the group box control. We have four choices for it : Flat, Popup, Standard ( default ), and System. If the group box is not visible ( value set to false ), then all the controls it contains also are not visible. - ٢٢ -

23 Questions 1) Multiple choice questions : If Then Else is a selection statement. a) single b) double c) triple d) None of the above. If Then is called a. Statement because it selects or ignores one action.. a) single-selection b) double-selection c) multiple-selection d) repetition. The operator returns False if the left operand is less than the right operand. a) = b) > c) d) All of the above. The if then Else selection statement ends with the keywords. a) End If b) End Else c) EndIf d) EndElse. The following shows a response only if the condition is equal to. If ( condition ) EndIf MsgBox( n is divisible d ) a) (n mod d) <> 0 b) (n \ d) = 0 c) (n mod d) = 0 d) (n\ d) <> 0 The property sets CheekBox's label. a) Label b) Text b) Checked d) Name The number of CheckBoxes that can be selected at once is equal to. a) 1 b) 2 c) 3 d) any number. - ٢٣ -

24 The condition (a AndAlso b) is True if. a) a is False and b is False b) a is False and is True c) A is True and b is False d) a is True and b is True. The condition (a Or Else b ) is False if. a) a is False and b is False b)a is True and b True c) a is True and b is False d) a is True and b is True. The condition (m Xor n ) is True if. a) m is True and n is True b) m is False and n is True c) m is True and n is False d) Both b and c. 2) Assume that a txtscore is a TextBox control and that the user entered the value 73.5 into the TextBox. Determine the action performed by the following code: 1 Dim score as Decimal 2 score = Decimal.Pares (textscore.text) 3 If score 90.0 Then 6 1b1Display. Text = Excellent 5 Else If score 75.0 Then. 6 lbldisplay. Text = Very Good 7 Else If score 60.0 Then 8 lbldisplay. Text = Good 9 Else If score 50.0 Then 10 lbldisplay. Text = Sufficient 11 Else 12 lbldisplay. Text = Insufficient 13 EndIf - ٢٤ -

25 Chapter 3: Repetition Statements Introduction All statements have been executed in order, from top to bottom, with two exceptions : the If, and Try / Catch. Now, we introduce the repetition statements, which are control statements that can repeat actions on a number of statements as long as a certain condition is True or False depending on the structure. The Do While..Loop Structure The top the loop Do while condition the loop continuation condition Statement 1 Statement Body of the Do While loop - Statement n Loop The bottom of the loop Each time the computer encounters Do While, it evaluates the condition If the condition is False, execution skips to the first statement following the reserved word Loop. If the condition is True, the computer executes theينفذ statements in the body of the loop from to bottom. 1- When Condition is False Do While condition Statement 1 Statement Body of the Do While loop - Statement n - ٢٥ -

26 Loop Statement x - ٢٦ -

27 2- When Condition is True Do While condition Statement 1 Statement Statement n Loop Statement x The For Next Loop Structure In contrast to the Do.. Loops, in which the number of repetitions of the loop body is unknown prior to processing. Note : The For Next Loop is used when we know the number of iterations of the loop in advance. L List Box Control One of the controls that are often associated with loops is the List Box. List Box appears as a rectangle that displays rows of text. Each row is an item that the user may select. The List Box properties Property Value Name (1 st.) Gets or sets the name of the control. Horizontal Scrollbar Gets or sets a Boolean value indicating whether a horizontal scroll is displayed in the control. Items Gets the items of the List Box. This property is itself an object that has its set of properties and methods. Selected Item Gets or sets the currently selected item in List Box. Sorted Gets or sets a Boolean value indicating whether the items in the List Box are sorted alphabetically regardless of the order they are entered. - ٢٧ -

28 List Box's Items property Method Add (text) Count Insert (index, text ) Remove (text) Remove At ( index ) Clear 0 Behavior Adds the text to the end of list of items Gets the number of items in the List Box Inserts the text at the index location indicated by index. The original item at that location and all items below it will be moved down to make room for the inserted item. Searches the items for an exact match of the text. It found that item is removed from the list and all items below it shift up one spot. Otherwise, nothing happens. Removes the item at the specific index value and all items below it shift up one spot. Removes all items from the List Box Questions 1- Multiple choice questions : 1.1 The body of a Do While Loop statement executes. a- Never b- at least once c- If its condition is True d- If its condition is False 1.2 Statements in the body of a Do Until Loop are executed repeatedly as long as the. remains False. a- Do loop condition b- loop continuation condition c- Until loop condition d- loop termination condition 1.3 The Statement executes until the loop continuation condition becomes False. a- Do Until.. Loop b- Do c- Do While d- Do While.. Loop 1.4 A. Is a variable that controls the number of times a number of statements will execute. a- repeater b- loop c- counter d- repetition control statement 1.5 Method.. deletes all the values in a List Box. a- Delete b- Clear c- Remove d- Destroy - ٢٨ -

29 1.6 Item's method adds an item to a List Box. a- Add b- Insert c- Include d- Append 2. Study the following code segment ( assume variable have been declared ) 1 Sum = 0 2 Count = 0 3 Do While ( x < 10 ) 4 Sum = sum + X 5 Count = count Loop 7 Average = sum / Count a- What is wrong with this code? b- Do steps to fix this code segment. Change x to COUNT 3. Find the error (s) in the following code. the loop should sum the numbers from 1 to 10 1 Dim x As Integer = 1 2 Dim Sum as Integer = 1 3 Do until x < = 10 4 Sum = sum + x 5 x = x Loop Change sign < to > 4. Consider the following code segment : 1 For I = To 10 Step X 2 Ms G Box (i) 3 Next Explain how loop will been have if : a. X is greater than 0 b. X is less than 0 c. X is equal to 0 Answer : a. will be executed b. not executed because ( X ) will be negative and the counter ( I ) well increase not decrease c. Will execute for only one time - ٢٩ -

30 5. Trace the following code segment, showing the value of each variable each time it changes : 1 X = For I = 0 To 7 Step 3 3 X = X* 2 4 Next Answer : I X X=4.5 For I = 0 to 7 step X = x * Next Convert the following for loop into a Do While Loop 1 For i = 1 To 10 2 Msg Box (i*i) 3 Next Answer : 1 Dim I as integer =1 2 Do while ( I < = 10 ) 3 MsgBox ( I * I ) 4 Loop 7. Describe the output from the following code segment 1 For i = 0 To 7 2 If (I / 2= 0 ) then 3 Msg Box (i+1) 4 Elself (I / 3= 0 ) then 5 Msg Box (i*i) 6 Elself (I / 5 = 0 ) then 7 Msg Box (2*i-1) 8 Else 9 Msg Box (i) 10 End If 11 Next Answer : The output will be as following : ( 1,1,2,3,4,5,6,7) - ٣٠ -

31 Chapter 4: Timers Introduction Events occur when the user takes an action like pressing a button or a radio Button. Sometimes we want to make events occur after some interval, without the user intervention. We can do that using Timer object Timer object : is an invisible stopwatch that gives you access to the system clock. The time interval for timer can be set using its Interval property. The time Interval can take the values 0 to 65,535 milliseconds, were one second is equal to 1,000 milliseconds. The timer Enable property has to be set to : 1- True to make the timer continuously running, (I) mean that the timer keeps firing every constant time period which is equal to its Interval property. 2- False to prevent the Tick event from occurring by setting the timer's Enabled property. The Enabled property default value is False, so you have to set it to True when you want to use the timer. The Date Time structure. Property Purpose Example Result Now Retrieve system date and time - ٣١ - X = Now 12/2/ :06:27PM Date Date Component x. Date 12/2/2008 Day Day of months: 1 31 x. Day 12 Day of Year Day of year : x. Day of Year 43 Hour Hour : 0 23 x. Hour 22 Minute Minute : 0 59 x. Minute 6 Second Second : 0 59 x. Second 27 Month Month ; 1= January x. Month 2 Add Days specified number of days later (or earlier ) x. Add Days (1) Add I day

32 Add Hours Specified number of hours later ( or earlier ) Add Minutes Specified a number of minutes later ( or earlier ) Note : x. Add Hours (5) x. Add Minutes ( 30 ) Add 5 hours x. Hour is equal to 22 because we are at 10o'clock P.M. Subtract 30 minutes Questions 1. Multiple choice questions : 1.1 Timer property Interval sets the rate a which Tick events occur in.. a- Seconds b- Milliseconds c- Nanosecond d- Microseconds 1.2 The.. Date structure retrieves your computer's date and time. a- Current Time b- Time c- Now d- Date Time 1.3 You can.. to a Date variable. a- Add days b- Add hours c- Subtract days d- All of the above 1.4 To subtract one day from Date variable X, assign the value returned by to X. a- X. Add Hours (-24) b- X. Subtract Days (1) c- X. Add Days (-1) d- All of the above 2. How long is an interval of 1500 seconds for a certain timer? 1500/1000 = 1.5 second 3. What fires a Timer's Tick event? To make enable property TRUE - ٣٢ -

33 THE COMPLETION OF THE BASIC EDUCATION CERTIFICATE Second Term Model 1 First Question: Put a tick ( ) in front of the true sentence and a cross (X) in front of the wrong sentence: 1- Variables of type Double, Single and Decimal allow storing fractional values, but with different degrees of precision. ( ) 2- When you declare a Variable, it is possible that the Variable Name begins with a number. ( ) 3-In (If Then ) statement, when the outcome of the condition is evaluated to be False then the statements following (Then) are executed. ( ) 4- The result of compound condition) X>=3 and Y<10) is True, if the two conditions are verified. ( ) 5-In (Do while Loop) statement, If the condition is evaluated to be True, execution of statements skips to the first statement following the reserved word (LOOP). ( ) 6- E prosecution is defined as sending a message by mistake to someone, you do not know ( ) Second Question: Choose the correct answer for each one of the following: 1- In For Next statement, the number of repetition in For X=1 to 8 step 3 is (a) 3 (b) 4 (c) 2 (d) 1 2- The property Interval for the (Timer) sets the rate at which the event occurs in (a) Second. (b) Minute. (c) Millisecond. (d) Hour. - ٣٣ -

34 3- We can stop the timer by giving the property the value false (a) Interval. (b) Enabled. (c) Modifiers (d) Tag 4- The Numeric Variable which takes integer numbers from 0 to 255 is.. (a) Integer. (b) String. (c) Byte. (d) Double. 5- One of the rules of naming the Variables or Constants in the program is: the variable name should start with.. (a) Number. (b) Any symbol. (c) Letter. (d) Space. Third Question: Rearrange the following steps in right order, to calculate the Sum of the odd numbers from 1 to 8: Loop Do While i <= 8 Dim i = 1, total As Integer Msgbox(total) total = total + i i = i + 2 Fourth Question: Choose from column b what is appropriate for coumn a: Column A Column B 1- DateTime (a) is used to repeat a group of command. 2- Const (b) is not equal. 3- For...Next (c) declaration of Constant. 4- Dim (d) equal. 5- Symbol <> is called (e) used with date and time (f) declaration of variable - ٣٤ -

35 First Question: THE COMPLETION OF THE BASIC EDUCATION CERTIFICATE Second Term Model 2 Put a tick ( ) in front of the true sentence and a cross (X) in front of the wrong sentence : 1-The result of executing the command MsgBox (5 + 3 ^ 2 / (8 mod 5)) gives 8 ( ) 2-Statements in the body of a (Do While.Loop), are executed only one time ( ) 3-(Timer) object can be used to execute a set of commands every constant period of time ( ) 4- You can use the (Text) property to write text inside the object (label1) or object (textbox1). ( ) Second Question: Complete the following statements from the words between brackets: 1- To delete all items from the object (listbox1), we use the method... ( Remove Clear Delete ) 2- To prevent the (Timer1) from running, you write the command " Timer1.enabled =.. " ( True False End ) 3- In (If Then Else ) statement, when the outcome of the condition is evaluated to be. then the statements following (Else) are executed ( True False Null ) 4- You can find out the date and time in the computer by executing the command MsgBox ( ) ( Now Time DateTime ) - ٣٥ -

36 Third Question: Use the figures and some of the words below to fill the spaces and complete the paragraph with true statements. CheckBox - RadioButton - second - first - TextBox The Design of Figure... is right where the tool... has been utilized to select one or more or none of the three foreign languages (English, French, and German) The design of Figure... is not right where the use of the tool... allow selecting only one language, from the three foreign languages. Fourth Question: Read the following code: Dim N, K, C As Integer C = 6 For N = 1 To 6 Step 3 K = K + N Next If N > C Then C = C + 1 End If Complete the following: 1- Value of the variable C is equal to Value of the variable N is equal to The result of the condition N> C is equal to Value of the variable K is equal to... - ٣٦ -

37 THE COMPLETION OF THE BASIC EDUCATION CERTIFICATE Second Term Model 3 First Question: State which of the following statements is (are) true or false 1- When the result of the conditional (Do while Loop) statement is True, then the statements inside the loop will be executed ( ) 2- The (For..Next ) statement continues to execute the statements as long as the starting value of the( iteration/repetition) is > 1 ( ) 3-The term "String" can be used as variable name to store string values assigned to (student names) ( ) 4-The (Timer) object can be used to execute a set of commands in constant time intervals ( ) 5- Anonymity is considered as form of Cyber bullying ( ) Second Question: Complete the following statements from the words between brackets. (Dim Const String - Single - Class Object) Khaled wants to write program codes to compute the total degrees of a student in all subjects, and 1-he uses numerical variable of type Single which is declared by the term ( ) 2-he uses also a variable type ( ) to store student name value. 3-he uses a variable of type ( ) to store the total degrees of the student in all subjects. - ٣٧ -

38 Third Question: Choose the suitable design from the two figures below: Fig (.). Fig ((1) ٢ ) Fig (2) Fourth Question: A) Read the following instructions Dim Age, Mark, Total As Single Age = 25.5 Mark = 90 If Age < 26 Then Age = 16 Mark=100 End If Total = Mark * 2 B) Execute the previous instructions,then choose the correct answers from the following: 1. The value of the variable "Age" is: a b -90 c The value of the variable "Mark" is: a 90 b-100 c The result of the condition Age < 26 : a 25.5 b- True c-false 4. The value of the variable "Total" is: a 200 b- 180 c- 190-٣٨ -

39 THE COMPLETION OF THE BASIC EDUCATION CERTIFICATE Second Term Model 4 First Question: Put a tick ( ) in front of the true sentence and a cross (X) in front of the wrong sentence: 1- The variable name "Spent_Money" is a valid name in terms of rules of naming variables. ( ) 2- The For Next Loop is used when we know in advance the number of iterations of the loop. ( ) 3-To clear the ListBox control from all items, the method Remove (text) is used.( ) 4-In a program, lines that begin with ('), are considered comments within the program code. ( ) 5-Variable of type Double is used to store integers only ( ) 6-Some forms of cyber bullying are the Outing of people through the dissemination of their private information. ( ) Second Question: Complete the following statements from the words between brackets: Is the range of values available for the numeric variable. (Accuracy - Range - The primary value of the variable) 2- Use a (Try / Catch) commands to... To detect errors and deal with it - to repeat the command a number of times - to repeat ) (the command once 3- The logical condition (M or N) will be wrong if... ( both N and M are false M is false,n is true both N and M are true ) 4- Statements written in the body of (Do While... Loop...) (are not implemented at all - are executed if the condition is True - are executed if the condition is False) 5- The Integer Division is expressed through (Div - \ - Mod ) 6- To prevent the occurrence of the event Tick so the Timer will be off, we set the property... a value False ( Interval - Enabled - Name ) - ٣٩ -

40 Third Question: 1- Write the scientific term for each phrase of the following statements: A: Method used to delete all items of the ListBox control is (...). B: Tool that allows programmers to divide a number of RadioButtons and CheckBoxes into different groups. (...). C: Tool that allows you to create or display a list of items (...). D: Tool that provide users with a range of alternatives to choose any of them at the same time. (..). 2- Read the following code: Dim X, Y, Z As Integer X = 2 Y = 3 Z = 4 MsgBox ( Y^X * X + Z * 3 ) And then type the result of the execution... : 2- Read the following code: Dim X, C As Integer X = 4 For C = 0 To 7 Step 3 X = X * 2 Next MsgBox ( X ) What is the value of x in the message box?... - ٤٠ -

41 THE COMPLETION OF THE BASIC EDUCATION CERTIFICATE Second Term Model 5 First Question: Put a tick ( ) in front of the true sentence and a cross (X) in front of the wrong sentence: 1- Variable of type Integer takes a range of integer numbers from 0 to 255. ( ) 2-The following names (Double, Single and Dim) can be used for naming Variables in program code. ( ) 3-If the variable A=20, variable B= 15 then the result of the condition A>=B is True. ( ) 4-In (Do while Loop) statement, execution of statements inside the loop are repeated until the condition in the Do While becomes False. ( ) 5-For the Variables of type Date, the subtraction of Days can be occurred. ( ) 6-You should remove immediately s sent from cyberbulling. ( ) Second Question: Complete the following statements from the words between brackets. (Dim Const String - Single - For Next) 1-To compute the total degrees of a student in all subjects, use numerical variable of type Single which is declared by the term ( ). 2-Also a variable type ( ) is used to store student name value. 3-Also a variable of type ( )is used to store the total degrees of the student in all subjects. 4-To declare constants, you can use the term ( ). 5-To repeat a set of commands, you can use ( ). - ٤١ -

42 Third Question: Rearrange the following steps in right order, to calculate the Sum of the odd numbers from 1 to 8: 1. total = total + i 2. Msgbox(total) 3. Next 4. For i = 1 To 8 Step 2 5. Dim i, total As Integer Fourth Question: Choose from column b what is appropriate for coumn a: Column A Column B 1- Count (A) is used to repeat a group of command. 2- Const (B) smaller than and equal. 3- Do While Loop (C) declaration of Constant. 4- Dim (D) greater than or equal. 5- Symbol >= is called (E) property used to identify the number of items in a Listbox tool (F) declaration of variable - ٤٢ -