Introduction to Programming in C

📘 Common C Interview Questions and Answers

In this chapter, we’ll cover frequently asked C programming interview questions along with concise explanations and code-based answers. These help you build confidence for both beginner and intermediate-level interviews.

🧠 Q1: What is the difference between == and = in C?

= is the assignment operator used to assign values.
== is the equality comparison operator.

int a = 5;        // assignment
if (a == 5) {...} // comparison

🧠 Q2: What is the use of static keyword?

• Inside functions: retains value between function calls
• At global scope: limits visibility to the file (internal linkage)

void countCalls() {
  static int count = 0;
  count++;
  printf("Called %d times\n", count);
}

🧠 Q3: Difference between call by value and call by reference

- Call by Value: copies actual value, changes don’t affect original.
- Call by Reference: passes address, changes reflect in the caller.

void change(int x) { x = 10; }         // value
void change(int *x) { *x = 10; }       // reference

🧠 Q4: What is a segmentation fault?

It occurs when your program tries to access unauthorized memory — often due to invalid pointers, uninitialized memory, or accessing freed memory.

🧠 Q5: Can we return an array from a function?

You cannot return arrays directly. Instead, return a pointer or use static/local array carefully.

int* getArray() {
  static int arr[5] = {1, 2, 3, 4, 5};
  return arr;
}

🧠 Q6: What are dangling pointers?

A pointer that refers to memory that has already been freed.

int *p = malloc(sizeof(int));
free(p);
*p = 20; // 🚨 Dangling pointer error

🧠 Q7: What is a memory leak?

If dynamically allocated memory is not freed using free(), it causes memory leaks which reduce available system memory.

🧠 Q8: Difference between struct and union

• struct: All members occupy their own memory.
• union: All members share the same memory space.

📚 UdaanPath Tip

Practice these questions regularly. Consider writing mini-code snippets in the C editor on UdaanPath.com or any online compiler to solidify your understanding.

📝 Bonus Practice Questions

• What is volatile keyword in C?
• What is recursion? Write a recursive factorial function.
• Difference between array and pointer?
• What is the output of printf("%d", printf("Hello"));?

✅ Summary

• We covered common theory and practical C interview questions
• Explained key concepts like pointers, memory, structs, recursion
• Used code snippets to back theoretical answers

🚀 Coming Next

Let's test your knowledge with a Final Quiz & Practice Set to ensure you’re ready to build with confidence and ace interviews.