Uninitialised values and booleans

Questions 1 to 5 of 7

1. 1. This program should count the values above 4, but it prints a different number on different runs. ``cpp #include <iostream> #include <vector> using namespace std; int main() { vector<int> values = {3, 8, 12, 5}; int big; for (int v : values) { if (v > 4) { ++big; } } cout << "values above 4: " << big << endl; } `` What is the fix?

   Change ++big to big = 1, so every match sets the count to oneChange v > 4 to v >= 4, so the test includes the value 4Change int big; to int big{};, so the counter starts at zeroChange vector<int> to a plain array, so the loop reads fixed memory
2. 2. This program should print full marks only when the score is 100. It prints full marks for a score of 75. ``cpp #include <iostream> using namespace std; int main() { int score = 75; if (score = 100) { cout << "full marks" << endl; } cout << "score is " << score << endl; } `` What is the bug?

   The score is an int, and it should be a doubleendl should be replaced with \n in both linesThe if should test score != 100, so that only other scores printThe if uses =, which stores 100 in score, when it should use == to compare
3. 3. This program should print any passed: true, because 72 and 91 pass. It prints any passed: false. ``cpp #include <iostream> #include <vector> using namespace std; int main() { vector<int> scores = {55, 72, 91, 40}; bool anyPassed = false; for (int s : scores) { anyPassed = s >= 60; } cout << boolalpha << "any passed: " << anyPassed << endl; } `` What is the bug?

   vector<int> cannot hold a list of test scoresThe assignment runs on every step, so the last score (40) overwrites the earlier passesboolalpha should be removed, so the flag prints as a numberThe >= should be >, so that a score of 60 counts as a pass
4. 4. A program declares int hits; outside every function, and int count; inside main. Both are read before anything sets them. Which statement is correct?

   hits starts at 0, and count holds leftover bitsBoth start at 0, because C++ clears every variableBoth hold leftover bits, because globals are never clearedhits holds leftover bits, and count starts at 0
5. 5. A program prints a bool variable done that is true, and the output is 1, not true. Which line is missing from the program?

   #include <bool>, which defines the bool typestd::cout << std::hex;, which prints numbers in base 16std::cout << std::boolalpha;, which makes bool values print as wordsbool done = 1;, which turns the value into a real bool