C Programming Questions and Answers – Unions – 2

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This set of C Multiple Choice Questions & Answers (MCQs) focuses on “Unions – 2”.

Pre-requisite for C Unions MCQ set: Video Tutorial on C Unions.

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1. What will be the output of the following C code?

  1.     #include <stdio.h>
  2.     union
  3.     {
  4.         int x;
  5.         char y;
  6.     }p;
  7.     int main()
  8.     {
  9.         p.x = 10;
  10.         printf("%d\n", sizeof(p));
  11.     }

a) Compile time error
b) sizeof(int) + sizeof(char)
c) Depends on the compiler
d) sizeof(int)
View Answer

Answer: d
Explanation: None.
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2. What will be the output of the following C code?

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  1.     #include <stdio.h>
  2.     union
  3.     {
  4.         int x;
  5.         char y;
  6.     }p;
  7.     int main()
  8.     {
  9.         p.y = 60;
  10.         printf("%d\n", sizeof(p));
  11.     }

a) Compile time error
b) sizeof(int) + sizeof(char)
c) Depends on the compiler
d) sizeof(char)
View Answer

Answer: c
Explanation: None.
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3. What will be the output of the following C code?

  1.     #include <stdio.h>
  2.     union p
  3.     {
  4.         int x;
  5.         char y;
  6.     };
  7.     int main()
  8.     {
  9.         union p p, b;
  10.         p.y = 60;
  11.         b.x = 12;
  12.         printf("%d\n", p.y);
  13.     }

a) Compile time error
b) Depends on the compiler
c) 60
d) Undefined behaviour
View Answer

Answer: c
Explanation: None.
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4. What will be the output of the following C code?

  1.     #include <stdio.h>
  2.     union p
  3.     {
  4.         int x;
  5.         char y;
  6.     }k = {1, 97};
  7.     int main()
  8.     {
  9.         printf("%d\n", k.y);
  10.     }

a) Compile time error
b) 97
c) a
d) 1
View Answer

Answer: d
Explanation: None.

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

  1.     #include <stdio.h>
  2.     union p
  3.     {
  4.         int x;
  5.         char y;
  6.     }k = {.y = 97};
  7.     int main()
  8.     {
  9.         printf("%d\n", k.y);
  10.     }

a) Compile time error
b) 97
c) a
d) Depends on the standard
View Answer

Answer: b
Explanation: None.

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

  1.     #include <stdio.h>
  2.     union p
  3.     {
  4.         int x;
  5.         float y;
  6.     };
  7.     int main()
  8.     {
  9.         union p p, b;
  10.         p.x = 10;
  11.         printf("%f\n", p.y);
  12.     }

a) Compile time error
b) Implementation dependent
c) 10.000000
d) 0.000000
View Answer

Answer: b
Explanation: None.

7. Which of the following share a similarity in syntax?

1. Union, 2. Structure, 3. Arrays and 4. Pointers

a) 3 and 4
b) 1 and 2
c) 1 and 3
d) 1, 3 and 4
View Answer

Answer: b
Explanation: None.

8. What will be the output of the following C code? (Assuming size of char = 1, int = 4, double = 8)

  1.     #include <stdio.h>
  2.     union utemp
  3.     {
  4.         int a;
  5.         double b;
  6.         char c;
  7.     }u;
  8.     int main()
  9.     {
  10.         u.c = 'A';
  11.         u.a = 1;
  12.         printf("%d", sizeof(u));
  13.     }

a) 1
b) 4
c) 8
d) 13
View Answer

Answer: c
Explanation: None.

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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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