C Programming Language

Union in C Language

⛪ Programming Language > C Programming Language

Union is an user defined datatype in C programming language. It is a collection of variables of different datatypes in the same memory location. We can define a union with many members, but at a given point of time only one member can contain a value. Unions can be very handy when you need to talk to peripherals through some memory mapped registers. ➲ Union in C Language - Quiz

Q 1: What is the similarity between a structure, union and enumeration?

  • A All of them let you define new values
  • B All of them let you define new data types
  • C All of them let you define new pointers
  • D All of them let you define new structures

Q 2: Size of a union is determined by 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

Q 3: Comment on the following union declaration? 

    #include <stdio.h>
    union temp
    {
        int a;
        float b;
        char c;
    };
union temp s = {1,2.5,'A'}; //REF LINE Which member of the union will be active after REF LINE?

  • A a
  • B b
  • C c
  • D Such declaration are illegal

Q 4: What would be the size of the following union declaration? 

    #include <stdio.h>
    union uTemp
    {
        double a;
        int b[10];
        char c;
    }u;
(Assuming size of double = 8, size of int = 4, size of char = 1)

  • A 4
  • B 8
  • C 40
  • D 80

Q 5: What type of data is holded by variable u int this C code? 

    #include <stdio.h>
    union u_tag
    {
        int ival;
        float fval;
        char *sval;
    } u;
The variable u here

  • 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

Q 6: 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

Q 7: What is the output of this C code? 
    #include "stdio.h"
    struct
    {
        char *name;
        union
        {
            char *sval;
        } u;
    } symtab[10];
the first character of the string sval by either of

  • 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].

Q 8: What is the output of this C code(size of int and float is 4)? 
    #include "stdio.h"
    union
    {
        int ival;
        float fval;
    } u;
    void main()
    {
        printf("%d", sizeof(u));
    }

  • A 16
  • B 8
  • C 4
  • D 32

Q 9: What is the output of this C code? 
    #include "stdio.h"
    union stu
    {
        int ival;
        float fval;
    };
    void main()
    {
        union stu r;
        r.ival = 5;
        printf("%d", r.ival);
    }

  • A 9
  • B Compile time error
  • C 16
  • D 5

Q 10: What will be the output of the program? 
#include"stdio.h"

int main()
{
    union a
    {
        int i;
        char ch[2];
    };
    union a u;
    u.ch[0]=3;
    u.ch[1]=2;
    printf("%d, %d, %d\n", u.ch[0], u.ch[1], u.i);
    return 0;
}

  • A 3, 2, 515
  • B 515, 2, 3
  • C 3, 2, 5
  • D 515, 515, 4

Q 11: What will be the output of the program? 
#include"stdio.h"

int main()
{
    union var
    {
        int a, b;
    };
    union var v;
    v.a=10;
    v.b=20;
    printf("%d\n", v.a);
    return 0;
}

  • A 10
  • B 20
  • C 30
  • D 0

Q 12: What will be the output of the program? 
#include"stdio.h"

int main()
{
    struct value
    {
        int bit1:1;
        int bit3:4;
        int bit4:4;
    }bit={1, 2, 13};

    printf("%d, %d, %d\n", bit.bit1, bit.bit3, bit.bit4);
    return 0;
}

  • A 1, 2, 13
  • B 1, 4, 4
  • C -1, 2, -3
  • D -1, -2, -13

Q 13: What will be the output of the program in 16 bit platform (Turbo C under DOS)? 
#include"stdio.h"

int main()
{
    struct value
    {
        int bit1:1;
        int bit3:4;
        int bit4:4;
    }bit;
    printf("%d\n", sizeof(bit));
    return 0;
}

  • A 1
  • B 2
  • C 4
  • D 9

Q 14: What will be the output of the program? 
#include"stdio.h"

int main()
{
    enum days {MON=-1, TUE, WED=6, THU, FRI, SAT};
    printf("%d, %d, %d, %d, %d, %d\n", MON, TUE, WED, THU, FRI, SAT);
    return 0;
}

  • A -1, 0, 1, 2, 3, 4
  • B -1, 2, 6, 3, 4, 5
  • C -1, 0, 6, 2, 3, 4
  • D -1, 0, 6, 7, 8, 9

Q 15: What will be the output of the program? 

#include<stdio.h>

int main()
{
    enum status {pass, fail, absent};
    enum status stud1, stud2, stud3;
    stud1 = pass;
    stud2 = absent;
    stud3 = fail;
    printf("%d %d %d\n", stud1, stud2, stud3);
    return 0;
}

  • A 0, 1, 2
  • B 1, 2, 3
  • C 0, 2, 1
  • D 1, 3, 2

Q 16: What will be the output of the program in Turbo C (under DOS)? 

#include<stdio.h>

int main()
{
    struct emp
    {
        char *n;
        int age;
    };
    struct emp e1 = {"Dravid", 23};
    struct emp e2 = e1;
    strupr(e2.n);
    printf("%s\n", e1.n);
    return 0;
}

  • A Error: Invalid structure assignment
  • B DRAVID
  • C Dravid
  • D No output

Q 17: What will be the output of the program in 16-bit platform (under DOS)? 

#include<stdio.h>

int main()
{
    struct node
    {
        int data;
        struct node *link;
    };
    struct node *p, *q;
    p = (struct node *) malloc(sizeof(struct node));
    q = (struct node *) malloc(sizeof(struct node));
    printf("%d, %d\n", sizeof(p), sizeof(q));
    return 0;
}

  • A 2, 2
  • B 8, 8
  • C 5, 5
  • D 4, 4

Q 18: What will be the output of the program? 

#include<stdio.h>

int main()
{
    struct byte
    {
        int one:1;
    };
    struct byte var = {1};
    printf("%d\n", var.one);
    return 0;
}

  • A 1
  • B -1
  • C 0
  • D Error

Q 19: What will be the output of the program? 

#include<stdio.h>

int main()
{
    enum days {MON=-1, TUE, WED=6, THU, FRI, SAT};
    printf("%d, %d, %d, %d, %d, %d\n", ++MON, TUE, WED, THU, FRI, SAT);
    return 0;
}

  • A -1, 0, 1, 2, 3, 4
  • B Error
  • C 0, 1, 6, 3, 4, 5
  • D 0, 0, 6, 7, 8, 9

Q 20: What will be the output of the program? 

#include<stdio.h>

    struct course
    {
        int courseno;
        char coursename[25];
    };
int main()
{
    struct course c[] = { {102, "Java"}, 
                          {103, "PHP"}, 
                          {104, "DotNet"}     };

    printf("%d ", c[1].courseno);
    printf("%s\n", (*(c+2)).coursename);
    return 0;
}

  • A 103 DotNet
  • B 102 Java
  • C 103 PHP
  • D 104 DotNet

Q 21: What will be the output of the program given below in 16-bit platform? 

#include<stdio.h>

int main()
{
    enum value{VAL1=0, VAL2, VAL3, VAL4, VAL5} var;
    printf("%d\n", sizeof(var));
    return 0;
}

  • A 1
  • B 2
  • C 4
  • D 10

Q 22: What is the output of this C code? 

    #include <stdio.h>
    union
    {
        int x;
        char y;
    }p;
    int main()
    {
        p.x = 10;
        printf("%d\n", sizeof(p));
    }

  • A Compile time error
  • B sizeof(int) + sizeof(char)
  • C Depends on the compiler
  • D sizeof(int)

Q 23: What is the output of this C code? 

    #include <stdio.h>
    union
    {
        int x;
        char y;
    }p;
    int main()
    {
        p.y = 60;
        printf("%d\n", sizeof(p));
    }

  • A Compile time error
  • B sizeof(int) + sizeof(char)
  • C Depends on the compiler
  • D sizeof(char)

Q 24: What is the output of this C code? 

    #include <stdio.h>
    union p
    {
        int x;
        char y;
    };
    int main()
    {
        union p p, b;
        p.y = 60;
        b.x = 12;
        printf("%d\n", p.y);
    }

  • A Compile time error
  • B Depends on the compiler
  • C 60
  • D Undefined behaviour

Q 25: What is the output of this C code? 

    #include <stdio.h>
    union p
    {
        int x;
        char y;
    }k = {1, 97};
    int main()
    {
        printf("%d\n", k.y);
    }

  • A Compile time error
  • B 97
  • C a
  • D 1

Q 26: What is the output of this C code? 

    #include <stdio.h>
    union p
    {
        int x;
        char y;
    }k = {.y = 97};
    int main()
    {
        printf("%d\n", k.y);
    }

  • A Compile time error
  • B 97
  • C a
  • D Depends on the standard

Q 27: What is the output of this C code? 

    #include <stdio.h>
    union p
    {
        int x;
        float y;
    };
    int main()
    {
        union p p, b;
        p.x = 10;
        printf("%f\n", p.y);
    }

  • A Compile time error
  • B Implementation dependent
  • C 10.000000
  • D 0.000000

Q 28: 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

Q 29: What is the output of this C code? 

    #include <stdio.h>
    union utemp
    {
        int a;
        double b;
        char c;
    }u;
    int main()
    {
        u.c = 'A';
        u.a = 1;
        printf("%d", sizeof(u));
    }
The output will be: (Assuming size of char = 1, int = 4, double = 8)

  • A 1
  • B 4
  • C 8
  • D 13

Q 30: What value will be printed for data.c? 
#include 
#include 
void main()
{
union Data{
	int i;
	unsigned char c;
}data;

data.c = 'C';
data.i = 89;
printf("%c\n", data.c);

}

  • A C
  • B Y
  • C G
  • D C89