C++ Programming MCQ – Namespaces

This section on C++ questions and puzzles focuses on “Namespaces”. One shall practice these questions and puzzles to improve their C++ programming skills needed for various interviews (campus interviews, walk-in interviews, company interviews), placements, entrance exams and other competitive exams. These programming puzzles can be attempted by anyone focusing on learning C++ programming language. They can be a beginner, fresher, engineering graduate or an experienced IT professional. Our C++ questions come with the detailed explanation of the answers which helps in better understanding of C++ concepts.

Here is a listing of C++ questions and puzzles on “Namespaces” along with answers, explanations and/or solutions:

1. Which operator is used to signify the namespace?
a) conditional operator
b) ternary operator
c) scope operator
d) bitwise operator
View Answer

Answer: c
Explanation: Scope operator(::) is used in namespace syntax.
General syntax:
namespace X{ int a;}
cout<<X::a;

2. Identify the correct statement.
a) Namespace is used to group class, objects and functions
b) Namespace is used to mark the beginning of the program
c) A namespace is used to separate the class, objects
d) Namespace is used to mark the beginning & end of the program
View Answer

Answer: a
Explanation: Namespace allows you to group class, objects, and functions. It is used to divide the global scope into the sub-scopes.

3. What is the use of Namespace?
a) To encapsulate the data
b) To structure a program into logical units
c) Encapsulate the data & structure a program into logical units
d) It is used to mark the beginning of the program
View Answer

Answer: b
Explanation: The main aim of the namespace is to understand the logical units of the program and to make the program so robust.
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4. What is the general syntax for accessing the namespace variable?
a) namespace::operator
b) namespace,operator
c) namespace#operator
d) namespace$operator
View Answer

Answer: a
Explanation: To access variables from namespace we use following syntax.
namespace :: variable;
General syntax:
namespace X{ int a;}
cout<<X::a;

5. What will be the output of the following C++ code?

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  1.     #include <iostream>
  2.     using namespace std;
  3.     namespace first
  4.     {
  5.         int var = 5;
  6.     }
  7.     namespace second
  8.     {
  9.         double var = 3.1416;
  10.     }
  11.     int main ()
  12.     {
  13.         int a;
  14.         a = first::var + second::var;
  15.         cout << a;
  16.         return 0;
  17.    }

a) 8.31416
b) 8
c) 9
d) compile time error
View Answer

Answer: b
Explanation: As we are getting two variables from namespace variable and we are adding that.
Output:

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$ g++ name.cpp
$ a.out
8

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6. What will be the output of the following C++ code?

  1.     #include <iostream>
  2.     using namespace std;
  3.     namespace first
  4.     {
  5.         int x = 5;
  6.         int y = 10;
  7.     }
  8.     namespace second
  9.     {
  10.         double x = 3.1416;
  11.         double y = 2.7183;
  12.     }
  13.     int main ()
  14.     {
  15.         using first::x;
  16.         using second::y;
  17.         bool a, b;
  18.         a = x > y;
  19.         b = first::y < second::x;
  20.         cout << a << b;
  21.         return 0;
  22.     }

a) 11
b) 01
c) 00
d) 10
View Answer

Answer: d
Explanation: We are inter mixing the variable and comparing it which is bigger and smaller and according to that we are printing the output.
Output:

$ g++ name1.cpp
$ a.out
10

7. What will be the output of the following C++ code?

  1.     #include <iostream>
  2.     using namespace std;
  3.     namespace Box1
  4.     {
  5.         int a = 4;
  6.     }
  7.     namespace Box2
  8.     {
  9.         int a = 13;
  10.     }
  11.     int main ()
  12.     {
  13.         int a = 16;
  14.         Box1::a;
  15.         Box2::a;
  16.         cout << a;
  17.         return 0;
  18.     }

a) 4
b) 13
c) 16
d) compile time error
View Answer

Answer: c
Explanation: In this program, as there is lot of variable a and it is printing the value inside the block because it got the highest priority.
Output:

$ g++ name2.cpp
$ a.out
16

8. What will be the output of the following C++ code?

  1.     #include <iostream>
  2.     using namespace std;
  3.     namespace space
  4.     {
  5.         int x = 10;
  6.     }
  7.     namespace space
  8.     {
  9.         int y = 15;
  10.     }
  11.     int main(int argc, char * argv[])
  12.     {
  13.         space::x = space::y =5;
  14.         cout << space::x << space::y;
  15.     }

a) 1015
b) 1510
c) 55
d) compile time error
View Answer

Answer: c
Explanation: We are overriding the value at the main function and so we are getting the output as 55.
Output:

$ g++ name4.cpp
$ a.out
55

9. What will be the output of the following C++ code?

  1.     #include <iostream>
  2.     using namespace std;
  3.     namespace extra
  4.     {
  5.         int i;
  6.     }
  7.     void i()
  8.     {
  9.         using namespace extra;
  10.         int i;
  11.         i = 9;
  12.         cout << i;
  13.     }
  14.     int main()
  15.     {
  16.         enum  letter { i, j};
  17.         class i { letter j; };
  18.         ::i();
  19.         return 0;
  20.     }

a) 9
b) 10
c) compile time error
d) 11
View Answer

Answer: a
Explanation: A scope resolution operator without a scope qualifier refers to the global namespace.

10. Which keyword is used to access the variable in the namespace?
a) using
b) dynamic
c) const
d) static
View Answer

Answer: a
Explanation: using keyword is used to specify the name of the namespace to which the variable belongs.
eg.
namespace A{ int a = 5;}
namespace B{ int a = 10;}
using namespace A;
cout<<a; // will print value of a from namespace A.
using namespace B;
cout<<a; // will print value of a from namespace B.

Sanfoundry Global Education & Learning Series – C++ Programming Language.

To practice all areas of C++ language, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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