Geeksquiz | Structure & Union

Structure & Union

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Structure & Union

Question 1

CORRECT

#include‹stdio.h›

intmain()

{

    structsite

    {

        charname[] = "GeeksQuiz";

        intno_of_pages = 200;

    };

    structsite *ptr;

    printf("%d ", ptr->no_of_pages);

    printf("%s", ptr->name);

    getchar();

    return0;

}

A

200 GeeksQuiz

B

200

C

Runtime Error

Compiler Error

Discuss it

Question 1 Explanation: 

When we declare a structure or union, we actually declare a new data type suitable for our purpose. So we cannot initialize values as it is not a variable declaration but a data type declaration.

Question 2

CORRECT

Assume that size of an integer is 32 bit. What is the output of following program?

#include<stdio.h>

structst

{

    intx;

    staticint y;

};

 

intmain()

{

    printf("%d",sizeof(structst));

    return0;

}

A

4

B

8

Compiler Error

D

Runtime Error

Discuss it

Question 2 Explanation: 

In C, struct and union types cannot have static members. In C++, struct types are allowed to have static members, but union cannot have static members in C++ also.

Question 3

CORRECT

structnode

{

   inti;

   floatj;

};

structnode *s[10];

The above C declaration define 's' to be (GATE CS 2000)

An array, each element of which is a pointer to a structure of type node

B

A structure of 2 fields, each field being a pointer to an array of 10 elements

C

A structure of 3 fields: an integer, a float, and an array of 10 elements

D

An array, each element of which is a structure of type node.

Discuss it

Question 4

WRONG

Consider the following C declaration

struct{

    shorts[5];

    union{

         floaty;

         longz;

    }u;

} t;

Assume that objects of the type short, float and long occupy 2 bytes, 4 bytes and 8 bytes, respectively. The memory requirement for variable t, ignoring alignment considerations, is (GATE CS 2000)

22 bytes

B

14 bytes

18 bytes

D

10 bytes

Discuss it

Question 4 Explanation: 

Short array s[5] will take 10 bytes as size of short is 2 bytes. When we declare a union, memory allocated for the union is equal to memory needed for the largest member of it, and all members share this same memory space. Since u is a union, memory allocated to u will be max of float y(4 bytes) and long z(8 bytes). So, total size will be 18 bytes (10 + 8).

Question 5

CORRECT

#include<stdio.h>

structst

{

    intx;

    structst next;

};

   

intmain()

{

    structst temp;

    temp.x = 10;

    temp.next = temp;

    printf("%d", temp.next.x);

    return0;

}

Compiler Error

B

10

C

Runtime Error

D

Garbage Value

Discuss it

Question 5 Explanation: 

A structure cannot contain a member of its own type because if this is allowed then it becomes impossible for compiler to know size of such struct. Although a pointer of same type can be a member because pointers of all types are of same size and compiler can calculate size of struct

Question 6

WRONG

Which of the following operators can be applied on structure variables?

A

Equality comparison ( == )

Assignment ( = )

C

Both of the above

None of the above

Discuss it

Question 6 Explanation: 

A structure variable can be assigned to other using =, but cannot be compared with other using ==

Question 7

CORRECT

uniontest

{

    intx;

    chararr[8];

    inty;

};

 

intmain()

{

    printf("%d",sizeof(uniontest));

    return0;

}

Predict the output of above program. Assume that the size of an integer is 4 bytes and size of character is 1 byte. Also assume that there is no alignment needed.

A

12

B

16

8

D

Compiler Error

Discuss it

Question 7 Explanation: 

When we declare a union, memory allocated for a union variable of the type is equal to memory needed for the largest member of it, and all members share this same memory space. In above example, "char arr[8]" is the largest member. Therefore size of union test is 8 bytes.

Question 8

WRONG

uniontest

{

    intx;

    chararr[4];

    inty;

};

 

intmain()

{

    uniontest t;

    t.x = 0;

    t.arr[1] ='G';

    printf("%s", t.arr);

    return0;

}

Predict the output of above program. Assume that the size of an integer is 4 bytes and size of character is 1 byte. Also assume that there is no alignment needed.

Nothing is printed

B

G

C

Garbage character followed by 'G'

D

Garbage character followed by 'G', followed by more garbage characters

Compiler Error

Discuss it

Question 8 Explanation: 

Since x and arr[4] share the same memory, when we set x = 0, all characters of arr are set as 0. O is ASCII value of '\0'. When we do "t.arr[1] = 'G'", arr[] becomes "\0G\0\0". When we print a string using "%s", the printf function starts from the first character and keeps printing till it finds a \0. Since the first character itself is \0, nothing is printed.

Question 9

WRONG

# include <iostream>

# include <string.h>

usingnamespace std;

 

structTest

{

  charstr[20];

};

 

intmain()

{

  structTest st1, st2;

  strcpy(st1.str,"GeeksQuiz");

  st2 = st1;

  st1.str[0] ='S';

  cout << st2.str;

  return0;

}

Segmentation Fault

B

SeeksQuiz

GeeksQuiz

D

Compiler Error

Discuss it

Question 9 Explanation: 

Array members are deeply copied when a struct variable is assigned to another one. See Are array members deeply copied? for more details.

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