Storage Classes in C MCQ Quiz – 10 Multiple Choice Questions with Answers

Storage Classes in C MCQ Quiz

Storage classes in C determine the scope, lifetime, visibility, and memory location of variables and functions. Understanding storage classes is essential for writing efficient programs and is a frequently asked topic in C programming interviews, Embedded Systems jobs, and technical assessments.

This Storage Classes in C MCQ Quiz contains carefully selected multiple-choice questions that help students and professionals evaluate their understanding of variable behavior in C programs.

Why Learn Storage Classes in C?

Storage classes play a critical role in memory management and program execution. They help programmers control:

• Variable scope
• Variable lifetime
• Memory allocation
• Accessibility across source files
• Program performance

The four primary storage classes in C are:

• Auto
• Static
• Extern
• Register

A strong understanding of these concepts is essential for Embedded Systems development, firmware programming, Linux device driver development, and general software engineering.

Storage Classes in C MCQ Questions and Answers

Question 1

What is the default storage class of a local variable in C?

a) static
b) extern
c) auto
d) register

Answer:
✅ c) auto

Explanation:
Local variables declared inside a function automatically belong to the auto storage class unless specified otherwise. These variables are created when the function starts execution and destroyed when the function exits.

Question 2

Which storage class retains the value of a variable between function calls?

a) auto
b) register
c) static
d) extern

Answer:
✅ c) static

Explanation:
A static variable is initialized only once and retains its value throughout the entire program execution, even after the function exits.

Question 3

What is the default value of a static variable if it is not explicitly initialized?

a) Garbage value
b) NULL
c) 0
d) 1

Answer:
✅ c) 0

Explanation:
Static variables are stored in the data segment and are automatically initialized to zero if no explicit value is assigned.

Question 4

Which storage class is used to access a global variable defined in another source file?

a) auto
b) register
c) static
d) extern

Answer:
✅ d) extern

Explanation:
The extern storage class tells the compiler that the variable is defined elsewhere and allows access across multiple source files.

Question 5

Where are auto variables typically stored?

a) Heap
b) Stack
c) Data Segment
d) CPU Register

Answer:
✅ b) Stack

Explanation:
Auto variables are generally stored in stack memory and exist only during the execution of the function where they are declared.

Question 6

Which of the following statements about register variables is true?

a) They always reside in CPU registers.
b) Their address can always be obtained using &.
c) They are suggested to be stored in CPU registers for faster access.
d) They retain their value between function calls.

Answer:
✅ c) They are suggested to be stored in CPU registers for faster access.

Explanation:
The register keyword is a request to the compiler to store the variable in a CPU register for faster access. The compiler may ignore this request if registers are unavailable.

Question 7

What will be the output of the following code?

void fun()
{
    static int x = 0;
    x++;
    printf("%d ", x);
}

int main()
{
    fun();
    fun();
    fun();
}

a) 1 1 1
b) 0 1 2
c) 1 2 3
d) 3 3 3

Answer:
✅ c) 1 2 3

Explanation:
The variable x is static, so it retains its value between function calls. The value increases with each call.

Question 8

Which storage class restricts a global variable’s visibility to the current source file?

a) extern
b) auto
c) register
d) static

Answer:
✅ d) static

Explanation:
A static global variable has internal linkage and can only be accessed within the source file in which it is declared.

Question 9

Which storage class does not allocate new memory for a variable?

a) auto
b) static
c) register
d) extern

Answer:
✅ d) extern

Explanation:
The extern declaration references an already existing variable rather than creating a new memory location.

Question 10

Which storage classes have a lifetime equal to the entire program execution?

a) auto and register
b) static and extern
c) auto and static
d) register and extern

Answer:
✅ b) static and extern

Explanation:
Variables declared using static and extern storage classes remain alive throughout the execution of the program.

Quick Revision Table

Real-World Applications of Storage Classes in C

Understanding storage classes is important in:

• Embedded Systems Programming
• Microcontroller Development
• RTOS-Based Applications
• Device Driver Development
• Automotive Embedded Software
• IoT Firmware Development
• Linux Embedded Systems
• Memory Optimization Techniques

Engineers frequently use static variables to retain state information, extern variables for cross-file communication, and register variables in performance-critical sections.

Key Takeaways

• Auto is the default storage class for local variables.
• Static variables preserve values between function calls.
• Extern allows access to global variables across files.
• Register suggests faster access using CPU registers.
• Storage classes determine scope, lifetime, visibility, and memory allocation.
• Storage class questions are commonly asked in Embedded Systems and C programming interviews.

Conclusion

This Storage Classes in C MCQ Quiz helps students, job seekers, and Embedded Systems enthusiasts assess their understanding of one of the most important concepts in C programming. Regularly practicing MCQ questions on storage classes improves problem-solving skills and strengthens interview preparation.

Continue practicing C programming quizzes to master memory management, variable scope, and program execution concepts that are essential in software and Embedded Systems development.