C Programming Questions and Answers – Unions – 1

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This set of C Multiple Choice Questions & Answers (MCQs) focuses on “Unions – 1”.

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

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1. The size of a union is determined by the size of the __________
a) First member in the union
b) Last member in the union
c) Biggest member in the union
d) Sum of the sizes of all members
View Answer

Answer: c
Explanation: None.

2. Which member of the union will be active after REF LINE in the following C code?

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  1.     #include <stdio.h>
  2.     union temp
  3.     {
  4.         int a;
  5.         float b;
  6.         char c;
  7.     };
  8.     union temp s = {1,2.5,’A’}; //REF LINE

a) a
b) b
c) c
d) Such declaration are illegal
View Answer

Answer: a
Explanation: None.
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3. What would be the size of the following union declaration? (Assuming size of double = 8, size of int = 4, size of char = 1)

  1.     #include <stdio.h>
  2.     union uTemp
  3.     {
  4.         double a;
  5.         int b[10];
  6.         char c;
  7.     }u;

a) 4
b) 8
c) 40
d) 80
View Answer

Answer: c
Explanation: None.
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4. What type of data is holded by variable u int in the following C code?

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  1.     #include <stdio.h>
  2.     union u_tag
  3.     {
  4.         int ival;
  5.         float fval;
  6.         char *sval;
  7.     } u;

a) Will be large enough to hold the largest of the three types;
b) Will be large enough to hold the smallest of the three types;
c) Will be large enough to hold the all of the three types;
d) None of the mentioned
View Answer

Answer: a
Explanation: None.

5. Members of a union are accessed as________________
a) union-name.member
b) union-pointer->member
c) both union-name.member & union-pointer->member
d) none of the mentioned
View Answer

Answer: c
Explanation: None.

6. In the following C code, we can access the 1st character of the string sval by using _______

  1.     #include <stdio.h>
  2.     struct
  3.     {
  4.         char *name;
  5.         union
  6.         {
  7.             char *sval;
  8.         } u;
  9.     } symtab[10];

a) *symtab[i].u.sval
b) symtab[i].u.sval[0].
c) You cannot have union inside structure
d) Both *symtab[i].u.sval & symtab[i].u.sval[0].
View Answer

Answer: d
Explanation: None.

7. What will be the output of the following C code (Assuming size of int and float is 4)?

  1.     #include <stdio.h>
  2.     union
  3.     {
  4.         int ival;
  5.         float fval;
  6.     } u;
  7.     void main()
  8.     {
  9.         printf("%d", sizeof(u));
  10.     }

a) 16
b) 8
c) 4
d) 32
View Answer

Answer: c
Explanation: None.

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

  1.     #include <stdio.h>
  2.     union stu
  3.     {
  4.         int ival;
  5.         float fval;
  6.     };
  7.     void main()
  8.     {
  9.         union stu r;
  10.         r.ival = 5;
  11.         printf("%d", r.ival);
  12.     }

a) 9
b) Compile time error
c) 16
d) 5
View Answer

Answer: d
Explanation: None.

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.

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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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