C Language Structures & Unions - Practice Questions 2026

Master C Language Structures and Unions: Practice Questions 2026

Welcome to the most comprehensive practice exam suite designed specifically to help you master C Language Structures and Unions. Whether you are a student preparing for academic exams or a developer aiming to sharpen your systems programming skills, these practice tests provide the rigorous training you need.

Why Serious Learners Choose These Practice Exams

Serious learners understand that watching a video is not the same as writing code. Mastery over C requires an intimate understanding of memory layout, padding, and data alignment. This course is designed to challenge your logic and force you to think like a compiler. By practicing with these exams, you ensure that you aren't just memorizing syntax, but truly grasping how C manages complex data types.

Course Structure

This practice suite is divided into logical tiers to ensure a smooth learning curve:

• Basics / Foundations: Focuses on the syntax of defining structures and unions. You will practice declaring variables, initializing members, and accessing them using the dot operator.

• Core Concepts: Delves into the fundamental differences between structures and unions. This section tests your knowledge of how memory is allocated for each member and the implications of sharing memory in a union.

• Intermediate Concepts: Covers nested structures, arrays of structures, and passing complex types to functions. You will also explore pointers to structures and the arrow (->) operator.

• Advanced Concepts: Challenges you with memory alignment, structure padding, and bit-fields. These are critical topics for low-level programming where every byte of memory counts.

• Real-world Scenarios: Presents problems modeled after actual engineering tasks, such as defining network packet headers, hardware registers, and file metadata formats.

• Mixed Revision / Final Test: A comprehensive simulation of a professional exam. This final tier mixes all previous topics to test your ability to switch context and solve complex problems under time pressure.

Sample Practice Questions

Question 1

What will be the output of the following C code?

C

struct Data {

    int i;

    char c;

};

struct Data d = {10, 'A'};

struct Data *ptr = &d;

printf("%d", ptr->i);

• Option 1: 10

• Option 2: A

• Option 3: Garbage Value

• Option 4: Compiler Error

• Option 5: Segmentation Fault

Correct Answer: Option 1

Correct Answer Explanation: In C, when you have a pointer to a structure, you access its members using the arrow operator (->). Here, ptr points to the structure d. Therefore, ptr->i correctly accesses the integer member i, which was initialized to 10.

Wrong Answers Explanation:

• Option 2: 'A' is the value of the member c, not i.

• Option 3: The variable is explicitly initialized to 10, so there is no reason for a garbage value.

• Option 4: The syntax is perfectly valid C code; there are no errors.

• Option 5: The pointer ptr is correctly assigned the address of d, so accessing it does not cause a segmentation fault.

Question 2

In a Union defined as union Shared { int a; char b; };, if you assign u.a = 65;, what will be the value of u.b on a typical system?

• Option 1: 0

• Option 2: 65

• Option 3: 'A'

• Option 4: Undefined

• Option 5: Compiler Error

Correct Answer: Option 3

Correct Answer Explanation: In a union, all members share the same memory location. The integer 65 corresponds to the ASCII value of the character 'A'. Since a and b share the same starting address, assigning 65 to a effectively places that bit pattern into the shared memory, which b interprets as 'A'.

Wrong Answers Explanation:

• Option 1: Memory is shared, so b will not remain 0 if a is modified.

• Option 2: While the numeric value is 65, the type of b is char, so it is interpreted as the character 'A'.

• Option 4: While the behavior of unions can be platform-dependent, the basic sharing of the first byte is well-defined in this context.

• Option 5: This is standard union usage and is perfectly legal in C.

Key Features of This Course

• You can retake the exams as many times as you want.

• This is a huge original question bank.

• You get support from instructors if you have questions.

• Each question has a detailed explanation.

• Mobile-compatible with the Udemy app.

• 30-days money-back guarantee if you are not satisfied.

We hope that by now you are convinced! And there are a lot more questions inside the course.