What does the following preprocessor do? #define OFFSET(type, field) ((size_t)&(((type *)0)->field))

The correct answer is A: It calculates the offset of a field in a structure. This macro calculates the byte offset of a field within a structure by casting 0 as a pointer to the type and taking the address of the field. Similar to the offsetof() macro in stddef.h.

What is the final value of x? int x = 0; for(int i = 1; i

The correct answer is A: 9. continue skips even values. x accumulates: 1(i=1) + 3(i=3) + 5(i=5) = 9. Values i=2,4 are skipped.

What is the size of the 'int' data type in a 32-bit system according to C standard?

The correct answer is D: Platform dependent. The size of 'int' is implementation-defined and depends on the compiler and platform, though it is typically 4 bytes on 32-bit systems.

Which memory segment stores global variables in C?

The correct answer is C: Data segment. Global variables are stored in the data segment (also called BSS segment for uninitialized globals). Local variables use the stack.

What is a potential issue when allocating very large contiguous blocks (>10^8 bytes) dynamically?

The correct answer is B: Fragmentation and allocation failure, should check return value. Large allocations may fail due to heap fragmentation or insufficient contiguous memory. Always check malloc() return for NULL.

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C Programming
Structures & Unions

C language from basics to advanced placement prep

34 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 34

Topics in C Programming

All Basics & Syntax 86 Data Types & Variables 97 Control Flow 100 Functions 99 Arrays & Strings 100 Pointers 99 Structures & Unions 100 File Handling 100 Dynamic Memory 98 Preprocessor 99

Q.11 Easy Structures & Unions

Which of the following is the correct way to initialize a structure in C?

A struct Point p = {10, 20};

B struct Point p; p = {10, 20};

C Point p = {10, 20};

D p.x = 10; p.y = 20; (without declaration)

Correct Answer: A. struct Point p = {10, 20};

EXPLANATION

Structures must be initialized at declaration time using curly braces. Assignment of initializer list is not valid after declaration.

Test

Q.12 Easy Structures & Unions

Which of the following correctly demonstrates a typedef for a structure?

A typedef struct { int x; int y; } Point;

B struct typedef Point { int x; int y; };

C define struct Point { int x; int y; };

D struct Point typedef { int x; int y; };

Correct Answer: A. typedef struct { int x; int y; } Point;

EXPLANATION

The correct syntax for typedef struct is: typedef struct { members } StructName;

Test

Q.13 Easy Structures & Unions

How do you access a member of a structure through a pointer in C?

A Using dot operator (.)

B Using arrow operator (->)

C Using asterisk (*)

D Using ampersand (&)

Correct Answer: B. Using arrow operator (->)

EXPLANATION

The arrow operator (->) is used to access structure members through a pointer. The dot operator is used with direct variables.

Test

Q.14 Easy Structures & Unions

Consider: union Data { int i; float f; char c; }; What is the size of this union?

A 4 bytes

B 9 bytes

C 5 bytes

D 12 bytes

Correct Answer: A. 4 bytes

EXPLANATION

The size of a union equals the size of its largest member. Here, int is 4 bytes (largest), so union size is 4 bytes.

Test

Q.15 Easy Structures & Unions

Which of the following statements about unions is correct?

A Union members share the same memory location

B Union size equals the sum of all member sizes

C All union members can hold values simultaneously

D Union requires more memory than structure

Correct Answer: A. Union members share the same memory location

EXPLANATION

Union members share the same memory location, and the union size equals the size of its largest member.

Test

Q.16 Easy Structures & Unions

What is the correct way to dynamically allocate an array of structures?
struct Student { int roll; char name[50]; };

A struct Student *arr = (struct Student*)malloc(n * sizeof(struct Student));

B struct Student arr = (struct Student*)malloc(n * sizeof(char));

C struct Student *arr = malloc(n);

D Student *arr = malloc(n * Student);

Correct Answer: A. struct Student *arr = (struct Student*)malloc(n * sizeof(struct Student));

EXPLANATION

Correct allocation requires pointer declaration, proper cast, and multiplying n with sizeof(struct Student).

Test

Q.17 Easy Structures & Unions

When structure is passed by value to a function, which of these is true?

A Changes to structure members inside function affect the original

B The entire structure is copied onto the stack

C Only pointers within the structure are copied

D Memory is shared between function and caller

Correct Answer: B. The entire structure is copied onto the stack

EXPLANATION

Pass by value creates a complete copy of the structure on the function's stack frame.

Test

Q.18 Easy Structures & Unions

Which of the following correctly demonstrates self-referential structure (for linked list)?

A struct Node { int data; struct Node *next; };

B struct Node { int data; Node *next; };

C struct Node { int data; *next; };

D Node { int data; Node *next; };

Correct Answer: A. struct Node { int data; struct Node *next; };

EXPLANATION

In C, self-referential structures require the struct keyword in pointer declarations within the structure definition.

Test

Q.19 Easy Structures & Unions

Which of these is a valid declaration of a structure variable using dot operator immediately after struct definition?

A struct Point { int x; int y; } p;

B struct Point { int x; int y; }; Point p;

C struct { int x; int y; } p;

D Both A and C

Correct Answer: D. Both A and C

EXPLANATION

Both methods are valid - A uses named struct tag with variable declaration, C uses anonymous struct with variable declaration.

Test

Q.20 Easy Structures & Unions

Consider union u { int i; char c; float f; }; What is the size of this union?

A 4 bytes

B 9 bytes

C 7 bytes

D Depends on compiler

Correct Answer: A. 4 bytes

EXPLANATION

Union size equals the largest member size. float is typically 4 bytes, which is largest.

Test

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