Submit your answers to these questions to the Curator under Quizzes as HW08 by the posted due date and time. No late submissions will be accepted.

Transcription

1 Instructions: For all questions, assume that any necessary header files have been included. Submit your answers to these questions to the Curator under Quizzes as HW08 by the posted due date and time. No late submissions will be accepted. For each of the questions 1 through 4, assume the FILE pointer Out is open on the file Out.txt, which is initially empty. Assume that the following variables are in scope: int A = ; double X = ; 1. What would the following statements write to Out.txt? Note: the first row of output is provided to make it easier to see the spacing that is used in the second line. fprintf(out, "%7d\n", A); 2. What would the following statements write to Out.txt? fprintf(out, "%9d\n", A); 3. What would the following statements write to Out.txt? fprintf(out, "%10.3f\n", X); )

2 4. What would the following statements write to Out.txt? fprintf(out, "%.8f\n", X); ) Assume the following variable declarations are in scope: int64_t B = 0; and assume the FILE pointer In is opened on a file which has the following contents: How should the blank in the following input statement be filled in order to read the value into the variable B? fscanf(in,, &B); 1) "%d" 2) "%"SCNd32 3) "%"SCNd64 4) "%"SCNu32 5) "%"SCNu64 6. Suppose the following array declaration and initialization is in scope: int A[5] = {1, 4, 9, 16, 25; Which of the following loops will write the contents of the array A as shown at right? 1) for (int i = 0; i < 5; i++) printf("%d:%d\n", i, A[i]); 2) for (int i = 1; i <= 5; i++) printf("%d:%3d\n", i, A[i]); 1: 1 2: 4 3: 9 4: 16 5: 25 3) for (int i = 0; i < 5; i++) printf("%d:%3d\n", i+1, A[i]); 4) for (int i = 1; i <= 5; i++) printf("%d:%3d\n", i, A[i-1]); 5) All of these 6) 1 and 3 only 7) 2 and 4 only 8) 3 and 4 only 9) None of these 2

3 For each of the questions 7 through 10, assume the FILE pointer In has just been opened on a file that contains: There are exactly 3 spaces between each pair of values. Assume that the following variables are in scope: int a, b, c, d, e; I advise experimentation on these questions! 7. What values will the following input statement assign to the variables? fscanf(in, "%d %d %d %d %d", &a, &b, &c, &d, &e); 8. What values will the following input statement assign to the variables? fscanf(in, "%2d %2d %2d %2d %2d", &a, &b, &c, &d, &e); 9. What values will the following input statement assign to the variables? fscanf(in, "%2d0 %2d0 %2d0 %2d0 %2d0", &a, &b, &c, &d, &e); 10. What values will the following input statement assign to the variables? fscanf(in, "%10d %10d %10d %10d %10d", &a, &b, &c, &d, &e); 3

4 A pentagonal number is one whose value can be represented by a nested pentagonal arrangement of dots. The first few pentagonal numbers are: 1: * 5: * 12: * 22: * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * The following incomplete C function is intended to test a value to see if it's a pentagonal number: // Determines whether N is a pentagonal number. // Pre: // N is initialized // Returns: true iff N is a pentagonal number // ispentagonal(uint32_t N) { // Line 1 uint32_t Sum = ; // 2 uint32_t Step = 1; // 3 while ( Sum < N ) { // 4 Sum = Sum + 2*Step + Step + 1; // 5 ++Step; // 6 return ; // 7 For questions 11 through 13, complete the given function by filling the blanks. 11. How should the blank in line 1 be filled? 1) bool 2) void 3) boolean 4) uint32_t 5) It should be left blank 12. How should the blank in line 2 be filled? 1) Sum does not need to be initialized. 2) 0 3) 1 4) 2 5) N 13. How should the blank in line 7 be filled? 1) true 2) false 3) Sum = N 4) Sum!= N 5) Step == N 4

5 The following incomplete C function is intended to swap the values of its two int parameters. That is, if the caller has two int variables A and B, a call Swap() can be used to swap the values of A and B. void Swap( x, y) { // 1 int temp = ; // 2 Back up first integer ; // 3 = temp; // 4 For questions 4 through 6, complete the given function by filling the blanks. 14. How should the blanks in line 1 be filled? (Both should be filled the same way.) 1) int 2) int* 3) int& 4) 2 or 3 only 15. How should the blank in line 2 be filled? 1) x 2) y 3) &x 4) &y 5) *x 6) *y 7) None of these 16. How should the blank in line 3 be filled? 1) x = y 2) y = x 3) &x = &y 4) &y = &x 5) *x = *y 6) *y = *x 7) None of these 17. Suppose you want to write a call to the function Swap() from the previous question, from the following code: int A = ; int B = 77; // place the call to Swap() here to swap values of A and B: Which of the following would be the correct way to write the call? 1) Swap(A, B); 2) Swap(B, A); 3) Swap(&A, &B); 4) Swap(&B, &A); 5) Swap(*A, *B); 6) Swap(*B, *A); 7) 1 and 2 only 8) 3 and 4 only 9) 5 and 6 only 10) None; none of the given choices will work. 5

6 18. If a C function has a return type that is not void, then: 1) The function should not take any parameters. 2) The function must take parameters. 3) Calls to the function should always be C statements, like: F( ); 4) Calls to the function should generally be the right side of an assignment statement, or occur as part of an expression. 19. The following function calculates the N-th Fibonacci number: // N: // FiboN: void fibonacci(uint64_t* FiboN, const uint32_t N) { if ( N <= 1 ) *FiboN = 1; uint64_t fnminustwo = 0; uint64_t fnminusone = 1; uint64_t fn; for (uint32_t i = 2; i <= N; i++) { fn = fnminusone + fnminustwo; fnminustwo = fnminusone; fnminusone = fn; *FiboN = fn; Suppose the caller has the following variables in scope: uint32_t N = 8; uint64_t FiboN; Which of the following would be the best way to make a call to the function fibonacci()? 1) fibonacci(fibon, N) 2) fibonacci(&fibon, N) 3) fibonacci(&fibon, &N) 4) fibonacci(*fibon, N) 5) fibonacci(*fibon, *N) 20. In the function fibonacci() above, the second parameter is declared as: const uint32_t N. What is the effect of the use of const for that parameter. 1) The caller cannot use a variable for that parameter when calling fibonacci(). 2) The function cannot modify the value of the parameter N. 3) If the call to the function looks like the code below, the function cannot modify the variable NN: uint32_t NN = 10; fibonacci(???, NN); 4) You cannot apply const to a parameter in this manner. 6