Chapter 3 Critical Thinking Questions s49s

Chapter 3 Critical Thinking Questions 1a) List four legal identifier names. Four legal identifier names are side, length, time, and mass. b) List four illegal identifier names and explain why each is illegal. i) Rectangle Area because there is a space between rectangle and area. ii) Rectangle.Perimeter because there is a period between rectangle and area. iii) $Money because there is a symbol in front of money, and it must start with a letter. iv) 5Five because there is a number in front of five, and it must start with a letter.

2a) In two statements, declare a variable named numCards and assign it the value 5. Dim numCards As Integer numCards = 5 b) In one statement, declare a variable named numCards and assign it the value 5. Dim numCards As Integer = 5

3a) What is the final value of yourNumber after the last statement executes? Dim myNumber As Integer = 5 Dim yourNumber As Integer = 4 myNumber = yourNumber * 2 yourNumber = MyNumber + 5 The final value of yourNumber is 13. b) What is the final value of yourNumber after the last statement executes? Dim myNumber As Integer Dim yourNumber As Integer = 4 myNumber = yourNumber + 7 yourNumber = mynumber

The final value of yourNumber is 11.

4) What is the primary purpose of a TextBox object? The primary purpose of a textbox object is to obtain input from the .

5) Why is the Val() function used in a statement that assigns the data from a text box to a numeric variable? The Val() function is used in a statement that assigns the data from a text box to a numeric variable to prevent a run-time error.

6a) What are labels near a text box called? Labels near a text box are called prompts. b) Why should text boxes have labels near them? Text boxes should have labels near them so the knows what kind of input is expected.

7) Determine the appropriate data type for each of the following values: a) the number of basketballs in a department store. Integer b) the price of a basketball. Decimal c) the number of players on a basketball team. Integer d) the average age of the players on a basketball team. Double e) whether a basketball player has received a jersey or not. Boolean f) the first initial of a basketball player’s first name. Char or Character

8) The statement Dim value As Integer = 3 appears in a Click event procedure for a button. The Click event procedure for a second button, contains the statements: Dim value As Integer Me.lvlOutput = value a) Is the scope of value local or global The scope is local because it is contained in a click event procedure.

b) What is shown in the label? Why? Nothing is shown in the label because the declaration statement is local in the first button, not the second button; therefore, there is no known value for the variable in the second button procedure.

9) What is the value of each of the following expressions? a) 10 / 5 * 4 = 8 b) 10 / 2 + 3 = 8 c) 6 Mod 3 + 4 = 4 d) 12 Mod 5 * 3 = 12 e) 12 Mod (5 * 3) = 12

10) What is the result of the following expression when x is 2005? When x is 1776? When x is 39? x = 2005 the result is 0 x = 1776 the result is 7 x = 39 the result is 3

11) Determine if each of the following are better represented by a variable or a constant and then write declarations using appropriate data types and descriptive identifiers: a) the number of votes received by an election candidate

Variable Dim Votes As Integer b) the percentage of votes won by a candidate Variable Dim VotePercent As Integer c) the first, middle, and last initials of an election candidate Constant Const FInital As Char Const MInital As Char Const LInitial As Char c) the year of the election Constant Const Year As Date = # 3/7/2017 #

12) For each of the following determine if the code contains a syntax error, logical error, or runtime error, and then correct the code. a) Dim num = 6 Logical error, change to Dim num As Integer = 6 b) Num = Value(Me.txtNum.Text) Syntax error, change it to Val(Me.txtNum.Text) c) lblOutput = message Syntax error, change it to lblOutput.text = message d) Dim test 1 As Integer Dim test 2 As Integer Dim avg As Double Test1 = Val(Me.txtTest1.Text) Test2 = Val(Me.txtText2.Text) Avg = test1 + test2 / 2 Logic error, change the Integer declarations to Double.

e) Dim numberTests As Integer Dim test1 As Integer = 80 Dim test2 As Integer = 88 Dim avg As Double Avg = (test1 + test2) / numberTests Logic error, you have to declare what numberTests is; for example, Dim numberTests As Integer = 2 f) Const MAX_CLASS_SIZE As Integer = 22 Dim currentSize As Integer currentSize = Val(Me.txtSize.Text) Me.lblEmptySeats.Text = MAX_CLASS_SIZE Logic error

13) What value is assigned to taxRate in the following statement if seven percent is typed in the txtTaxRate text box? TaxRate = Val(Me.txtTaxRate.Text) 0 shows up if seven percent is typed in the txtTaxRate text box. 14) Write each equation as a Visual Basic assignment statement, assuming π is a constant named PI: a) A = lw A=l*w b)

P=

R−C N

P = (R – C) / N c)

a=

h (b 1+b 2) N

A = H *(B1 + B2) / N

d)

4 πr 3

3

4 / 3 * PI * R ^ 3

F +S +T 3

e) A=

A = (F + S + T) f)

P=

5F 4D2

P = (5*F) / (4*D ^ 2) g) A = P +Prt A = P + (Pr * t) h) M =

Pr ( 1+ r ) n ( 1+r ) n−1

M = (Pr * (1 + R) ^ n) / ((1 + r) ^ n – 1) i)

x=

−b √ b 2−4 ac 2a

X = (-b * (b ^2 – 4*a*c)^ 1/2) / (2 * a)

15) Rewrite the equations in parts (a) through (h) of question 14 to solve for the variable listed below and then write each equation as a Visual Basic assignment statement: a) l l=A/W b) R R = (P * N) – C c) b1 b1 = (A * N / H) – b2 d) r r = (V / (4/3 * PI)) ^ 1/3 e) T T = (A * 3) - F – T

f) F F = (P * 4D^2) / 5 g) P P = A / Prt h) P P = (M * (1 + r)^ n – 1) / (r * (1+r)^n) 16) Determine if each of the following statements is true or false. If false, explain why. a) A variable must be declared before used. True b) Multiple variable with different data types can be declared in a single statement. False, multiple variables with the SAME data types can be declared in one statement.

c) A runtime error results in the termination of program execution. True d) The Val() function converts textbox data to a string value. False, it converts it to a numeric value. e) An integer variable uses 4 bytes of memory to store its value. True f) Boolean variables are initialized to true. False, they are initialized to true. g) In the variable statement x = 4.5, where x is an Integer variable, x is assigned the value 4. True h) Modulus division returns the remainder resulting from divison. True i) In the variable assignment x = 14 Mod 4 * 2, where x is a Double variable, x is assigned the value 4. True

j) Constant declarations must be placed in the beginning of the program. False, they do not have to be placed in the beginning; however, it is preferred to have a broader scope. k) Visual Basic sees no difference between the variables NEW and New. True l) Keywords make good variable identifiers. False, keywords cannot be used as identifiers.

m) Private is a keyword. True n) The Visual Basic IDE informs the programmer of a syntax error. True o) Errors that violate the rules of Visual Basic are called semantic errors. False, they are errors that are caused by statements that produce undesired results. p) Run-time errors are always detected by the complier. False, run time errors are errors not detected by the complier. q) A breakpoint temporarily stops the execution of a program, but pressing the right arrow key continues the execution. False, the F8 key is used to resume the execution.