CSCI 3327 Visual Basic Chapter 4: Control Statements in Visual Basic (Part 1B) UTPA – Fall 2011

Objectives In this chapter, you will do exercises related to: –Primitive data types in Visual Basic –Arithmetic operators –Algorithm design –Usage of control structures in Visual Basic 2

Compound Assignment Operators Value = Value + 3  Value +=3 More compound assignment operators – += – -= – *= – /= – \= – ^= – &= 3

Example 3.8: Addition.vb URL: p_2010/codeexamples.html p_2010/codeexamples.html TextBox –Change the names of controls E.g., resultLabel, number1TextBox, number2TextBox, addButton –resultLabel.Text = "The sum is" & total –TextChanged Events –Clear() method 4

Exercises The form's _____ property specifies the text that is displayed in the Form's title bar. –1. Title 2. Text 3. (Name) 4. Name Property _____ specifies how text is aligned within a Label's boundaries –1. Alignment 2. AlignText 3. Align 4. TextAlign An output Label should ______. –1. be distinguishable from other Labels –2. initially have an empty Text property or a default value –3. use Fixed3D for the BorderStyle property –4. All of the above A Button's ______ property sets the text on the face of the Button. –1. Name 2. Text 3. Title 4. Face If there are errors in an application, they appear in a window known as the _____. –1. TaskList 2. Output 3. Properties 4. Error List 5

Exercises (cont'd) When a value is placed into a memory location, the value ______ the previous value in that location. –1. copies 2. replaces 3. adds itself to 4. moves When a value is read from memory, that value is _____. –1. overwritten 2. replaced with a new value 3. moved to a new location in memory 4. not overwritten Arithmetic expressions must be written ___to facilitate entering applications into the computer. –1. using parentheses 2. on multiple lines 3. in straight-line form 4. None of the above The expression to the right of an assignment operator (=) is evaluated ______the assignment occurs. –1. before 2. after 3. at the same time 4. none of the above 6

True/False Statements Comments cause the computer to print the text after the ' on the screen when the program executes. All variables must be declared before they can be used in a Visual Basic program. Visual Basic considers the variable names number and NuMbEr to be different. The arithmetic operators *, /, + and – all have the same level of precedence. A string of characters contained between double quotation marks is called a phrase or phrase literal. Integer division yields an Integer result. 7

What Does the Code Do? Dim number1 As Integer Dim number2 As Integer Dim result As Integer number1 = 5*(4+6) 'What is number1? number2= 2^2 'What is number2? result =number1 \ number2 'What is result? 8

What is Wrong in the Code? Dim number1 As Integer Dim number2 As Integer Dim result As Integer number1 = (4*6^4)/(10 Mod 4 - 2) number2=(16\3)^2*6+1 result =number1-number2 9

Exercises A(n) ______ is a plan for solving a problem in terms of the actions to be executed and the order in which these actions are to be executed. –1. chart 2. control structure 3. algorithm 4. ordered list ____ is an informal language that helps you develop algorithms. –1. Pseudocode 2. VB-Speak 3. Notation 4. None of the above Pseudocode_____. –1. usually describes only declarations 2. is executed on computers 3. usually describes only executable lines of code 4. usually describes declarations and executable lines of code All Visual Basic applications can be written in terms of ___ types of control structures. –1. one 2. two 3. three 4. four 10

Exercises (cont'd) The process of application statements executing one after another in the order in which they are written is called_______. –1. transfer of control 2. sequential execution 3. workflow 4. none of the above The symbol _____ is not a Visual Basic operator. –1. * 2. ^ 3. % 4. <> If … Then …Else is a ______-selection statement. –1. single 2. double 3. triple 4. nested If "number" is initialized with the value 5, what value will "number" contain after the expression: number-=3 executes? –

Exercises (cont'd) The body of a Do While … Loop statement executes ______. –1. at least once 2. never 3. while its condition is true 4. while its condition is false Statements in the body of a Do until … Loop execute repeatedly for as long as the _____ remains False. –1. loop-continuation condition 2. do-loop condition 3. loop-termination condition 4. until-loop condition 12

Exercises (cont'd) Identify errors in the code that totals the values from 1 to 50, assuming that value is 50. –Do While value >=0 – sum+=value –Loop 13

Exercises (cont'd) Write a repetition structure that obtains 2^10 (DO NOT use ^ directly). 14

True/False Statements Pseudocode is a structured programming language. The body of a Do While … Loop is executed only if the loop-continuation test is false. The body of a While … End While is executed only if the loop-continuation test is false. The body of a Do Until … Loop is executed only if the loop-termination test is false. 15

Exercises After the Class Chapters 1~4 in your textbook –Self-Review Exercises –Quick Quiz –Exercises 16