Q: How do you link a C++ program to C functions?
A: By using the extern "C" linkage specification around the C function declarations.
Q: Explain the scope resolution operator.
A: It permits a program to reference an identifier in the global scope that has been hidden by another identifier with the same name in the local scope.
Q: What are the differences between a C++ struct and C++ class?
A: The default member and base-class access specifiers are different.
Q: How many ways are there to initialize an int with a constant?
A: Two.
There are two formats for initializers in C++ as shown in the example that follows. The first format uses the traditional C notation. The second format uses constructor notation.
int foo = 123;
int bar (123);
Q: How does throwing and catching exceptions differ from using setjmp and longjmp?
A: The throw operation calls the destructors for automatic objects instantiated since entry to the try block.
Q: What is your reaction to this line of code?
delete this;
A: It’s not a good practice.
Q: What is a default constructor?
A: A constructor that has no arguments.
Q: What is a conversion constructor?
A: A constructor that accepts one argument of a different type.
Q: What is the difference between a copy constructor and an overloaded assignment operator?
A: A copy constructor constructs a new object by using the content of the argument object. An overloaded assignment operator assigns the contents of an existing object to another existing object of the same class.
Q: When should you use multiple inheritance?
A: There are three acceptable answers: "Never," "Rarely," and "When the problem domain cannot be accurately modeled any other way."
Q: What is a virtual destructor?
A: The simple answer is that a virtual destructor is one that is declared with the virtual attribute.
Q: Explain the ISA and HASA class relationships. How would you implement each in a class design?
A: A specialized class "is" a specialization of another class and, therefore, has the ISA relationship with the other class. An Employee ISA Person. This relationship is best implemented with inheritance. Employee is derived from Person. A class may have an instance of another class. For example, an employee "has" a salary, therefore the Employee class has the HASA relationship with the Salary class. This relationship is best implemented by embedding an object of the Salary class in the Employee class.
Q: When is a template a better solution than a base class?
A: When you are designing a generic class to contain or otherwise manage objects of other types, when the format and behavior of those other types are unimportant to their containment or management, and particularly when those other types are unknown (thus, the genericity) to the designer of the container or manager class.
Q: What is a mutable member?
A: One that can be modified by the class even when the object of the class or the member function doing the modification is const.
Q: What is an explicit constructor?
A: A conversion constructor declared with the explicit keyword. The compiler does not use an explicit constructor to implement an implied conversion of types. It’s purpose is reserved explicitly for construction.
Q: What is the Standard Template Library?
A: A library of container templates approved by the ANSI committee for inclusion in the standard C++ specification.
A programmer who then launches into a discussion of the generic programming model, iterators, allocators, algorithms, and such, has a higher than average understanding of the new technology that STL brings to C++ programming.
Q: Describe run-time type identification.
A: The ability to determine at run time the type of an object by using the typeid operator or the dynamic_cast operator.
Q: What problem does the namespace feature solve?
A: Multiple providers of libraries might use common global identifiers causing a name collision when an application tries to link with two or more such libraries. The namespace feature surrounds a library’s external declarations with a unique namespace that eliminates the potential for those collisions.
This solution assumes that two library vendors don’t use the same namespace identifier, of course.
Q: Are there any new intrinsic (built-in) data types?
A: Yes. The ANSI committee added the bool intrinsic type and its true and false value keywords.
6 Comments on Advanced C++ and STL interview questions
I like the template that you have used, its easy on the eyes.
Differance btw C++ structs and Classes:
Structs have data members as Public by default and Classes have data members as Private be default.
l suggest that you publish problems helping a learner going through
c++ problems &java in the accademic sphere ande not employment sphere.
A google search turned up this page from you site about C++ questions:
http://www.techinterviews.com/?p=9
I found that some of the questions had faulty wording or faulty answers. They were:
Q: Explain the scope resolution operator.
Your answer was egregiously over-limiting, since the 99% of the time the scope resolution operator is *not* used to access a variable in global scope. More often it is used to access static class members and types. See the “scope” entry in the index in Stroustrup’s C++ 3rd edition, and notice the subheading “resolution operator” points to page 228, where this by far most common usage is exampled.
Q: How does throwing and catching exceptions differ from using setjmp and longjmp?
This isn’t really a C++ question per se (you are mixing in WinTel issues). Your question should instead be something like, “What are the keywords for exception handling?” Or for an advanced question: “Should exception objects be passed by value or by reference to a catch block? Why?”
Q: What is a conversion constructor?
C++ doesn’t have anything officially called a “conversion constructor”. Thats just an idiom that a few people *might* use. Suggest dropping the question.
Q: When is a template a better solution than a base class?
Groan. This question is like asking “When is medicine better than atoms?” Worse, the answer you gave didn’t even address base classes. To fix this question and answer, all you need to do is change the question to this “When is a template an appropriate tool to use?”
Q: Are there any new intrinsic (built-in) data types?
Bad question. “new” as compared to what, the “C” language? Your publication claims to test C++ knowledge, not “C++ compared to C” knowledge. And even if you are talking about new types from an older C++ to a newer C++, I’m not sure your question / answer is relevant. It seems to me that bool was “added” back in 1994, which is so darn long ago that calling bool a “new” intrinsic type makes your test sound very, very dated.
-Brent Arias
> Q: What is a default constructor?
> A: A constructor that has no arguments.
Default constructor WITH arguments
class B {
public:
B (int m = 0) : n (m) {}
int n;
};
int main(int argc, char *argv[])
{
B b;
return 0;
}
Most of these comments are picky-une at best.
The one about the difference between setjmp() and longjmp() vs. C++ exception handling mixing in a *WINTEL* issue (???) is a real piece’a work. (:O
Most of the peanut gallery’s “corrections” are themselves flawed (e.g., difference between a C++ class vs. struct is that *ALL* members [not just data members] have a different access level]). Keep up the good work and may you grow a thicker skin.
I was about to point some BETTER answers (e.g., the scope resolution operator is used to override default scope [broader than just global access]; and also: the default constructor is a constructor that *CAN* *BE* called without any arguments, etc.), but for the most part, this is pretty good stuff. I wish your answer regarding “delete this” was a little sterner (explaining WHY it is bad practise: it presumes the object was allocated from the heap; moreover, exposes the likely design flaw that *somebody* knows more about destroying the object than the class’s destructor itself).
Keep up the good work.