Appendix D: Interview Questions

Table of Contents

• Table of Contents
• D.1 Basic Questions
• D.2 Intermediate Questions
• D.3 Advanced Questions
• D.4 Exercises
• D.5 Solutions
  • D.5.1 Solution 1
  • D.5.2 Solution 2
  • D.5.3 Solution 3
  • D.5.4 Solution 4
  • D.5.5 Solution 5
  • D.5.6 Solution 6
  • D.5.7 Solution 7
  • D.5.8 Solution 8

D.1 Basic Questions

1. What is a pointer?
2. How do you declare an array in C?

D.2 Intermediate Questions

1. What is the difference between malloc and calloc?
2. How do you pass a function as a parameter in C?

D.3 Advanced Questions

1. Explain undefined behavior with an example.
2. What is memory alignment and why is it important?

D.4 Exercises

1. Write a function to reverse a string in C.
2. What happens if you free the same pointer twice?

D.5 Solutions

D.5.1 Solution 1

A pointer is a variable that stores the address of another variable.

D.5.2 Solution 2

int arr[10]; declares an array of 10 integers.

D.5.3 Solution 3

malloc allocates uninitialized memory; calloc allocates zero-initialized memory.

D.5.4 Solution 4

Use a function pointer: void func(void (*fptr)()) { fptr(); }

D.5.5 Solution 5

Undefined behavior: e.g., accessing an array out of bounds. The result is unpredictable.

D.5.6 Solution 6

Memory alignment ensures data is stored at addresses suitable for the hardware, improving performance and avoiding faults.

D.5.7 Solution 7

void reverse(char *str) {
    int n = strlen(str);
    for (int i = 0; i < n/2; i++) {
        char tmp = str[i];
        str[i] = str[n-1-i];
        str[n-1-i] = tmp;
    }
}

D.5.8 Solution 8

Freeing the same pointer twice causes undefined behavior (often a crash).