3. Can every Do-Loop loop be written as a For-Next loop? Why or why not? 4. Name two types of files that can be opened and used in a VB program.

Transcription

1 CE 311 K Fall 005 Second Exam - Examples Answers at the bottom. 1. What are two categories of flow control structures?. Name three logical operators in Visual Basic (VB). 3. Can every Do-Loop loop be written as a For-Next loop? Why or why not?. Name two types of files that can be opened and used in a VB program. 5. Name two different types of subprograms. 6. What does it mean to pass a parameter by reference? by value? 7. Write VB statements to: a) Open a sequential file for input: b) Open a sequential file for output: 8. Write an appropriate If-Then statement or an If-Then-Else block for the following situation: Test the value of the variable sum. If sum exceeds 100, then display its value, adjust its value so that it equals 100 and assign the string Maximum Amount Exceeded to the string variable Flag. 9. Write a loop that will calculate the sum of every third integer, beginning with i = (i.e., calculate the sum ) for all values of i that are less than 100. Write the loop in each of the following ways: Using a For-Next Loop structure Using a Do While Loop structure 10. Write a Visual Basic program to evaluate the algebraic formula log( t p( t) = log( t a) ) if t if t > a a where t is a number that a user enters and a = 100. Use: a. A text box for input. b. A picture box for output. c. A function procedure to evaluate the algebraic formula: CE311K McKinney 1 10/10/005

2 11. Find the products AB and BA if they are defined: 5 A = B = Consider the following program Private sub cmdcommand_click() End sub Dim k as integer, m as integer, n as integer Open C:\Input.dat for Input as #1 Open C:\Output.dat for Output as # Input #1, n, m k = (n * n) + m * m * m Print #, k If the values of and 3 are read for n and m, respectively, what value is printed for k? 13. State whether and why the following program segments will print r, z, or nothing for the values r = 10.0, z =.0. a. If (r * z) >=.0 Then r; z; nothing picoutput.print r Why? Else picoutput.print z b. If (r = z) Then r; z; nothing picoutput.print r Why? c. If (r + z) >= 1.0 Then r; z; nothing picoutput.print r Why? CE311K McKinney

3 1. Write Visual Basic statements to carry out the following flow chart: Is a < 0? Print a is nonnegative Print a is negative 15. Are the following logical expressions true or false when i = 0 and a = 10.5? a. (i <= 0) OR (a > 1.0) True; False b. NOT (i = 0) True; False c. i = 0 AND a > 10.0 OR a < 9.0 True; False 16. If a = 1, b =, and c = 3, what are the values of a, b, and c at the end of the following program segment? If a <= b Then If c > Then c = If c < 3 Then a = 0 Else b = What are the values of r and s at the conclusion of each of the following loops if r = 0.0 and s =.0 when the loops begin. a. For i = 1 to 5 r = r = r + s s = s * s s = Next i CE311K McKinney 3

4 b. Do While s <= 100 r = r = r + s s = s * s s = Loop 18. If i = 0 and g = 5, what are the values of i and g after the following program segment? Do while i <= AND g > 0 i = i + 1 g = g 1.0 Loop i = g = 19. The series for cos(x) is x cos( x) = 1! + x! n n ( 1) x + L + +L (n)! Write a program to approximate cos(x) using k terms of this series. You may assume that the following function has already been written and is available for you to use in your program as you like: Private Function factorial(n As Integer) As single Dim i As single, x As single x = 1 For i = To n x = x * i Next factorial = x End Function 0. Consider the following three matrices, A, B, and C. 3 5 A = =, B 5, a. Find the Product D = A * B C = 3 5 b. Find the Sum E = D + C c. Find the Transpose of E CE311K McKinney

5 ANSWERS 1. Selection and repetition. AND, OR, NOT 3. No. A Do loop can be controlled by a logical condition with no specified number of times through the loop, whereas, a For loop needs to have a definite countable number of times that it will execute.. Sequential and Random Access 5. Subprocedure and function 6. Reference passing parameter s address in memory. Value passing parameter s numerical value 7. a) Open filename as #1 for Input b) Open filename as #1 for Output 8. If (sum > 100) Then picoutput.print sum sum = 100 Flag = Maximum Amount Exceeded 9. Using a For-Next Loop structure Sum = 0 For i = To 100 Step 3 sum = sum + i Next i Using a Do While Loop structure 10. i = sum = 0 Do Sum = sum + i i = i + 3 While (i < 100) Sub Program Dim a as double Dim t as Double t = txt1.text picoutput.print p = ; p(t, a) End Sub Function p(t as double, a as double) as double If( t*t > a) then p = log(t^ a) Else CE311K McKinney 5

6 11. p = log(t^) End Function AB = BA is undefined 5 *1 + * + *8 + 5*9 86 = = 8 3*1+ 1* + 0*8 + 9* 5 9 CE311K McKinney 6