81. Which of these is not a valid C++ logical operator?
- a) &&
- b) ||
- c) !
- d) &|
Answer: D - &| is not a valid operator in C++ (it's sometimes used in other languages).
82. What is the correct syntax to declare a friend function?
- a) friend void func(); inside class
- b) void friend func(); inside class
- c) friend void func() { } inside class
- d) Both a and b
Answer: D - The friend keyword can appear before or after the return type in the declaration.
83. Which of the following is true about inline functions?
- a) They must be defined in header files
- b) They are always faster than regular functions
- c) They are suggestions to the compiler
- d) They cannot be recursive
Answer: C - inline is a hint to the compiler, which may ignore it.
84. What is the output of: cout << (7 % 4);
- a) 1
- b) 2
- c) 3
- d) 4
Answer: C - % is the modulus operator (remainder of 7 divided by 4 is 3).
85. Which of these is not a valid C++17 feature?
- a) if constexpr
- b) Structured bindings
- c) std::filesystem
- d) Concepts
Answer: D - Concepts were introduced in C++20.
86. What is the purpose of the '[[nodiscard]]' attribute?
- a) To prevent function inlining
- b) To warn when return value is ignored
- c) To disable return value optimization
- d) To mark functions as pure
Answer: B - [[nodiscard]] warns if a function's return value is ignored.
87. Which STL container provides fastest lookup by key?
- a) std::vector
- b) std::map
- c) std::unordered_map
- d) std::list
Answer: C - unordered_map provides O(1) average case lookup using hashing.
88. What is the correct way to declare a static member variable?
- a) static int x; inside class
- b) int static x; inside class
- c) static int x; outside class
- d) Both a and b
Answer: D - static can appear before or after the type in the declaration.
89. Which of these is not a valid C++ type trait?
- a) std::is_integral
- b) std::is_class
- c) std::is_functional
- d) std::is_pointer
Answer: C - is_functional is not a standard type trait.
90. What is the output of: cout << sizeof(std::string);
- a) 4
- b) 8
- c) 16
- d) Implementation defined
Answer: D - std::string size depends on the implementation (typically 24-32 bytes).
91. Which of these is not a valid C++20 feature?
- a) Concepts
- b) Ranges
- c) Coroutines
- d) Reflection
Answer: D - Reflection is planned for future C++ versions.
92. What is the purpose of the '[[likely]]' attribute?
- a) To mark code paths more likely to execute
- b) To indicate thread safety
- c) To force inlining
- d) To disable optimizations
Answer: A - [[likely]] helps compiler optimize for the expected path.
93. Which STL algorithm is used to count elements?
- a) std::find
- b) std::count
- c) std::search
- d) std::accumulate
Answer: B - std::count counts elements matching a value.
94. What is the correct way to declare a nested namespace?
- a) namespace A { namespace B { } }
- b) namespace A::B { }
- c) Both a and b
- d) nested namespace A::B { }
Answer: C - Both syntaxes are valid (the second requires C++17).
95. Which of these is not a valid C++14 feature?
- a) Binary literals
- b) Generic lambdas
- c) Variable templates
- d) Modules
Answer: D - Modules were introduced in C++20.
96. What is the output of: cout << (10 / 3);
- a) 3
- b) 3.333
- c) 3.0
- d) 4
Answer: A - Integer division truncates the fractional part.
97. Which of these is not a valid C++ container?
- a) std::forward_list
- b) std::flat_map
- c) std::unordered_set
- d) std::multimap
Answer: B - flat_map is not in the standard (though available in some libraries).
98. What is the purpose of the '[[no_unique_address]]' attribute?
- a) To allow empty class optimization
- b) To prevent address-taking
- c) To mark singleton classes
- d) To disable RTTI
Answer: A - It enables empty base optimization for data members.
99. Which STL algorithm is used to merge sorted ranges?
- a) std::merge
- b) std::concat
- c) std::join
- d) std::combine
Answer: A - std::merge combines two sorted ranges into one sorted range.
100. What is the correct way to declare a deduction guide?
- a) template<typename T> MyClass(T) -> MyClass<T>;
- b) MyClass template<T>(T) -> MyClass<T>;
- c) deduce MyClass(T) -> MyClass<T>;
- d) template<T> MyClass(T) -> MyClass<T>;
Answer: A - Deduction guides follow template declaration syntax.