C Pointers Interview Questions 2026: 30 Q&A With Code

Last Updated: June 2026 | Level: Freshers to Mid-Level | Read Time: ~16 min

In C, pointers are everything: arrays, strings, dynamic memory, and callbacks all run through them. Candidates report that pointer arithmetic, the array-pointer relationship, and malloc/free are guaranteed for embedded and core-CS interviews. This guide covers 30 C pointer questions with full answers and predict-the-output traps. Behaviour reflects the official C language references; confirm any memory semantics on the standard.

Pair this with C Programming Placement Questions and C Output Prediction Questions 2026.

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Table of Contents

1. Pointer Basics (Q1 to Q9)
2. Arrays and Strings (Q10 to Q18)
3. Dynamic Memory (Q19 to Q24)
4. Function Pointers and Advanced (Q25 to Q30)
5. Predict the Output
6. Quick Revision Table
7. Frequently Asked Questions

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Pointer Basics

Q1. What is a pointer in C? Easy

int x = 10;
int *p = &x;
printf("%d", *p);   // 10

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Q2. What is the size of a pointer? Medium

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Q3. What is a null pointer? Easy

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Q4. What is a dangling pointer? Medium

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Q5. What is a wild pointer? Easy

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Q6. What is pointer arithmetic? Medium

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Q7. What is a void pointer and its limitation? Medium

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Q8. What is the difference between *p++ and (*p)++? Hard

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Q9. What is a double pointer? Medium

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Arrays and Strings

Q10. What is the relationship between arrays and pointers? Medium

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Q11. Why is sizeof(array) different from sizeof(pointer)? Hard

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Q12. How are strings represented in C? Easy

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Q13. What is the difference between char arr[] and char *p for strings? Hard

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Q14. How do you pass an array to a function? Medium

void print(int *a, int n) {
  for (int i = 0; i < n; i++) printf("%d ", a[i]);
}

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Q15. What is pointer to an array vs array of pointers? Hard

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Q16. How do you iterate a string using pointers? Medium

char *s = "abc";
while (*s) { putchar(*s); s++; }

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Q17. What does the array name evaluate to? Medium

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Q18. Can you change where an array name points? Easy

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Dynamic Memory

Q19. What are malloc, calloc, realloc, and free? Medium

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Q20. What is the difference between malloc and calloc? Medium

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Q21. What happens if you free the same pointer twice? Hard

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Q22. What is a memory leak in C? Easy

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Q23. Should you cast the result of malloc? Hard

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Q24. What does realloc return on failure? Medium

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Function Pointers and Advanced

Q25. What is a function pointer? Medium

int add(int a, int b) { return a + b; }
int (*fp)(int, int) = add;
printf("%d", fp(2, 3));   // 5

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Q26. How is qsort implemented with function pointers? Hard

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Q27. What is a pointer to a const vs a const pointer? Hard

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Q28. What is the difference between pass by value and pass by pointer? Medium

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Q29. How do you swap two integers using pointers? Medium

void swap(int *a, int *b) {
  int t = *a; *a = *b; *b = t;
}

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Q30. What is the difference between stack and heap memory? Medium

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Predict the Output

Snippet 1

int a[] = {1, 2, 3};
int *p = a;
printf("%d %d", *(p + 1), *p + 1);

Output:

2 2

Why: *(p+1) is the second element (2). *p + 1 is the first element (1) plus 1, also 2 here. Precedence trap that interviewers vary.

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Snippet 2

char *s = "hello";
printf("%c", *(s + 1));
printf("%lu", sizeof(s));

Output:

e8

Why: *(s+1) is 'e'. sizeof(s) is the pointer size (8 on 64-bit), not the string length.

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Snippet 3

int x = 5, *p = &x, **pp = &p;
**pp = 20;
printf("%d", x);

Output:

20

Why: Double dereference writes through pp to p to x, setting it to 20.

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Quick Revision Table

Concept	Key takeaway
array decays	name becomes pointer in expressions
sizeof array vs pointer	full size vs pointer size
char[] vs char* literal	modifiable vs read-only
malloc vs calloc	garbage vs zeroed
double free	undefined, set NULL after free
const placement	read right to left
pass by pointer	enables modifying caller's variable

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Frequently Asked Questions

What C pointer topic is asked most in 2026?

Candidates report that pointer arithmetic, the relationship between arrays and pointers, and dynamic memory with malloc and free are the most repeated C pointer questions for embedded and core-CS roles.

Why are pointers so heavily tested in C interviews?

Because C has no references or smart pointers, so pointers are the only indirection mechanism. Understanding them is essential for arrays, strings, dynamic memory, and function callbacks.

What is the most common C pointer bug?

Dereferencing a dangling or uninitialised pointer, followed by memory leaks from forgetting free and buffer overruns from bad pointer arithmetic. Interviewers test all three.

What is the difference between char arr[] and char *p for a string?

char arr[] copies the literal into a modifiable array, while char *p points to a read-only string literal whose modification is undefined behaviour. Use the array form when you need to edit the string.

Why should I assign realloc to a temporary first?

Because realloc returns NULL on failure while leaving the original block valid. Assigning directly to the same pointer would overwrite it with NULL on failure and leak the original allocation.

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Related Articles

• C Programming Placement Questions, the master set
• C Output Prediction Questions 2026, tricky snippets
• C++ Pointers Interview Questions 2026, pointers in C++
• Data Structures Interview Questions 2026, pointer-based structures

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Confirm any pointer or memory semantics on the official C language references before your interview. This guide reflects candidate-reported patterns and public preparation resources as of June 2026.