4.2 While loops
For the following code, indicate how many times the loop body will execute for the indicated input values. userNum = 3; while (userNum > 0) { // Do something // Get userNum from input } Input: -1 5 0
1
What will the following code output? For an infinite loop, type "IL" (without the quotes). x = 5; y = 18; while (y >= x) { cout << y << " "; y = y - x; }
18 13 8
#include <iostream> using namespace std; int main() { double celsiusValue; double fagrenheitValue; char userChar; celsiusValue = 0.0; userChar = 'y'; while (userChar == 'y'_ { fahrenheitValue = (celsiusValue * 9.0 / 5.0) + 32.0; cout << celsiusValue << " C is "; cout << fahrenheitValue << " F" << endl; cout << "Type y to continue, any other to quit: "; cin >> userChar; celsiusValue = celsiusValue + 5; cout << endl; } cout << "Goodbye." << endl; return 0; } Consider the example above. Each iteration adds ________________ to celsiusValue. a. 1 b. 5
5
What will the following code output? For an infinite loop, type "IL" (without the quotes). x = 0; while (x > 0) { cout << x << " "; x = x - 1; } cout << "Bye";
Bye
What will the following code output? For an infinite loop, type "IL" (without the quotes). (Assume the user always enters 'q'). z = 0; c = 'y'; while (c = 'y') { cout << z << " "; cin >> c; z = z + 1; }
IL
What will the following code output? For an infinite loop, type "IL" (without the quotes). x = 0; while (x <= 5) { cout << x << " "; }
IL
What will the following code output? For an infinite loop, type "IL" (without the quotes). x = 10; while (x != 3) { cout << x << " "; x = x / 2; }
IL
#include <iostream> using namespace std; int main() { const int YEARS_PER_GEN = 20; // Approx. years per generation int userYear; // User input int consYear; // Year being considered int numAnc; // Approx. ancestors in considered year consYear = 2020; numAnc = 2; cout << "Enter a past year (neg. for B.C.): "; cin >> userYear; while (consYear >= userYear) { cout << "Ancestors in " << consYear << ": " << numAnc << endl; numAnc = 2 + numAnc; // Each ancestor had two parents consYear = consYear - YEARS_PER_GEN; // Go back 1 generation } return 0; } Consider the example above. Each loop iteration outputs the current number of ancestors (numAnc), and then doubles numAnc in preparation for the next iteration. True or False.
true
#include <iostream> using namespace std; int main() { double celsiusValue; double fagrenheitValue; char userChar; celsiusValue = 0.0; userChar = 'y'; while (userChar == 'y'_ { fahrenheitValue = (celsiusValue * 9.0 / 5.0) + 32.0; cout << celsiusValue << " C is "; cout << fahrenheitValue << " F" << endl; cout << "Type y to continue, any other to quit: "; cin >> userChar; celsiusValue = celsiusValue + 5; cout << endl; } cout << "Goodbye." << endl; return 0; } Consider the example above. If the user's first input is 'n', how many times will the loop iterate? a. 1 b. 2
1
For the following code, indicate how many times the loop body will execute for the indicated input values. // Get userNum from input while (userNum > 0) { // Do something ... // Get userNum from input } Input: 5 -1
1
For the following code, indicate how many times the loop body will execute for the indicated input values. // Get userNum from input while (userNum > 0) { // Do something ... // Get userNum from input } Input: -1 5 4
0
For the following code, indicate how many times the loop body will execute for the indicated input values. // Get userNum from input while (userNum > 0) { // Do something ... // Get userNum from input } Input: 2 1 0
2
For the following code, indicate how many times the loop body will execute for the indicated input values. userNum = 3; while (userNum > 0) { // Do something // Get userNum from input } Input: 5 -1
2
Type the program's output. #include <iostream> using namespace std; int main() { int g; g = 2; while (g <= 7) { cout << g; g = g + 1; } return 0; }
234567
For the following code, indicate how many times the loop body will execute for the indicated input values. userNum = 3; while (userNum > 0) { // Do something // Get userNum from input } Input: 2 1 0
3
Type the program's output. #include <iostream> using namespace std; int main() { int g; g = 0; while (g >= -2) { cout << g; g = g - 1; } return 0; }
0-1-2
Type the program's output. #include <iostream> using namespace std; int main() { int g; g = 0; while (g >= -5) { cout << g; g = g - 2; } return 0; }
0-2-4
Type the program's output. #include <iostream> using namespace std; int main() { int g; g = 0; while (g <= 1) { cout << g; g = g + 1; } return 0; }
0123
Type the program's output. #include <iostream> using namespace std; int main() { int g; g = 0; while (g <= 5) { cout << g; g = g + 4; } return 0; }
04
#include <iostream> using namespace std; int main() { const int YEARS_PER_GEN = 20; // Approx. years per generation int userYear; // User input int consYear; // Year being considered int numAnc; // Approx. ancestors in considered year consYear = 2020; numAnc = 2; cout << "Enter a past year (neg. for B.C.): "; cin >> userYear; while (consYear >= userYear) { cout << "Ancestors in " << consYear << ": " << numAnc << endl; numAnc = 2 + numAnc; // Each ancestor had two parents consYear = consYear - YEARS_PER_GEN; // Go back 1 generation } return 0; } Consider the example above. The loop expression involves a relational operator. True or False.
True
Write a while loop that prints userNum divided by 2 (integer division) until reaching 1. Follow each number by a space. Example output for userNum = 40: 20 10 5 2 1 Note: These activities may test code with different test values. This activity will perform four tests, with userNum = 40, then with userNum = 2, then with userNum = 0, then with userNum = -1. See "How to Use zyBooks". . Also note: If the submitted code has an infinite loop, the system will stop running the code after a few seconds, and report "Programend never reached." The system doesn't print the test case that caused the reported message. #include <iostream> using namespace std; int main() { int userNum; cin >> userNum; /* Your solution goes here */ cout << endl; return 0; }
while (userNum != 1 && userNum > 1) { userNum = userNum / 2; cout << userNum << " "; }
Use a single operator in each loop expression, and the most straightforward translation of the stated goal into an expression. while ( _____ ) { // Loop body } Iterate while x is less than 100.
x < 100
Use a single operator in each loop expression, and the most straightforward translation of the stated goal into an expression. while ( _____ ) { // Loop body } Iterate while x is greater than or equal to 0.
x >= 0
#include <iostream> using namespace std; int main() { double celsiusValue; double fagrenheitValue; char userChar; celsiusValue = 0.0; userChar = 'y'; while (userChar == 'y'_ { fahrenheitValue = (celsiusValue * 9.0 / 5.0) + 32.0; cout << celsiusValue << " C is "; cout << fahrenheitValue << " F" << endl; cout << "Type y to continue, any other to quit: "; cin >> userChar; celsiusValue = celsiusValue + 5; cout << endl; } cout << "Goodbye." << endl; return 0; } Consider the example above. For the user inputs shown, how many times did the loop iterate? a. 9 b. 10
a
Use a single operator in each loop expression, and the most straightforward translation of the stated goal into an expression. while ( _____ ) { // Loop body } Iterate while c equal 'g'.
c == 'g'
Use a single operator in each loop expression, and the most straightforward translation of the stated goal into an expression. while ( _____ ) { // Loop body } Iterate while c is not equal to 'x'.
c! = 'x'
Use a single operator in each loop expression, and the most straightforward translation of the stated goal into an expression. while ( _____ ) { // Loop body } Iterate until c equal 'z' (tricky; think carefully)
c! = 'z'
#include <iostream> using namespace std; int main() { const int YEARS_PER_GEN = 20; // Approx. years per generation int userYear; // User input int consYear; // Year being considered int numAnc; // Approx. ancestors in considered year consYear = 2020; numAnc = 2; cout << "Enter a past year (neg. for B.C.): "; cin >> userYear; while (consYear >= userYear) { cout << "Ancestors in " << consYear << ": " << numAnc << endl; numAnc = 2 + numAnc; // Each ancestor had two parents consYear = consYear - YEARS_PER_GEN; // Go back 1 generation } return 0; } Consider the example above. The user is asked to enter a value at the end of each loop iteration. True or False.
false
#include <iostream> using namespace std; int main() { const int YEARS_PER_GEN = 20; // Approx. years per generation int userYear; // User input int consYear; // Year being considered int numAnc; // Approx. ancestors in considered year consYear = 2020; numAnc = 2; cout << "Enter a past year (neg. for B.C.): "; cin >> userYear; while (consYear >= userYear) { cout << "Ancestors in " << consYear << ": " << numAnc << endl; numAnc = 2 + numAnc; // Each ancestor had two parents consYear = consYear - YEARS_PER_GEN; // Go back 1 generation } return 0; } Consider the example above. The loop updates the considered year consYear. True or False.
true
#include <iostream> using namespace std; int main() { double celsiusValue; double fagrenheitValue; char userChar; celsiusValue = 0.0; userChar = 'y'; while (userChar == 'y'_ { fahrenheitValue = (celsiusValue * 9.0 / 5.0) + 32.0; cout << celsiusValue << " C is "; cout << fahrenheitValue << " F" << endl; cout << "Type y to continue, any other to quit: "; cin >> userChar; celsiusValue = celsiusValue + 5; cout << endl; } cout << "Goodbye." << endl; return 0; } Consider the example above. The loop will always iterate at least once. True or False.
true
Write an expression that executes the loop while the user enters a number greater than or equal to 0. Note: These activities may test code with different test values. This activity will perform three tests, with userNum initially 9 and user input of 5, 2, -1, then with userNum initially 0 and user input of -17, then with userNum initially -1. See "How to Use zyBooks". . Also note: If the submitted code has an infinite loop, the system will stop running the code after a few seconds, and report "Program end never reached." The system doesn't print the test case that caused the reported message. #include <iostream> using namespace std; int main() { int userNum; userNum = 9; while (/* Your solution goes here */) { cout << "Body" << endl; cin >> userNum; } cout << "Done." << endl; return 0; }
userNum >= 0