C Language Interview Questions

Here you get a free C Language Interview Question which helps you to Give Correct Answer of the Question in the Interview. It also helps you for you college exams Preparation.

Basic of C & Data Types

1. Explain the purpose of the sizeof operator in C. How does it differ for different data types?
2. How does the C compiler handle type conversions between data types?
3. What are type qualifiers (const, volatile, restrict) in C?
4. Why are signed and unsigned important in data type declarations?
5. How are variables stored in memory, and what determines their addresses?
6. What are auto, register, static, and extern storage classes?
7. Explain typecasting in C and when you would use it.
8. Describe the purpose and use of the void data type.
9. How is a structure different from a union in terms of memory allocation?
10. How do you implement and use enumerated data types (enum) effectively?

Operators and Expressions

1. Explain the difference between postfix (i++) and prefix (++i) operators.
2. Describe how short-circuit evaluation works with logical operators.
3. How does operator precedence affect expression evaluation?
4. Write a function to use bitwise operators to swap two numbers without using a third variable.
5. Explain the concept of “undefined behavior” with operator usage.
6. How does the comma operator work in C?
7. Why would you use the ternary operator instead of an if-else?
8. How can bitwise operators help in optimizing mathematical operations?
9. What are the limitations of using shift operators on signed integers?
10. How can you use the bitwise XOR operator to perform encryption and decryption?

Control Structures and Flow Control

1. What is the difference between if-else if-else and nested if statements?
2. How does switch work internally, and how does it handle fall-through cases?
3. What happens if you do not include a break statement in switch cases?
4. Write a program that uses nested loops to create a pattern in the console.
5. What are labeled statements, and how are they used with goto?
6. Explain the advantages and disadvantages of using goto statements.
7. How does the continue statement work in nested loops?
8. Write a function using for, while, and do-while to reverse an integer.
9. Describe how you would implement a menu-driven program using switch.
10. How can return statements be used to terminate a function and return values?

Functions

1. How do function pointers work, and when are they useful?
2. Explain recursion and how it can be used in C programming.
3. Describe the difference between call-by-value and call-by-reference.
4. How do inline functions work in C? When would you use them?
5. Write a function to calculate the nth Fibonacci number using recursion.
6. What are static functions, and how are they different from global functions?
7. How does variable scope impact function design?
8. Explain how variadic functions (like printf) are implemented in C.
9. Write a function that calculates factorial using both recursion and iteration.
10. What is a re-entrant function, and why is it significant?

Pointers

1. Explain pointer arithmetic and how it operates with arrays.
2. What is a NULL pointer, and when would you use it?
3. Write a program to swap two variables using pointers.
4. How are pointers to functions used, and why are they helpful?
5. Describe what double pointers (**) are and how to use them.
6. Explain the concept of pointer dereferencing and its risks.
7. What is memory alignment, and how does it affect pointers?
8. How do you dynamically allocate memory for an array using pointers?
9. Describe how const can be used with pointers.
10. Write a program that demonstrates pointer to pointer operations.

Arrays and Strings

1. How does C handle arrays in memory?
2. Explain the difference between a one-dimensional and multi-dimensional array.
3. Write a function to reverse a string in place.
4. How can you use pointers to iterate through an array?
5. What are the limitations of array bounds in C?
6. How is a string represented in C, and how does it differ from other languages?
7. Write a function that searches for a substring within a string.
8. Explain how arrays are passed to functions.
9. What is the difference between a static and dynamic array?
10. Describe how you would handle memory for dynamically allocated strings.

Dynamic Memory Management

1. How does malloc work, and what are its limitations?
2. Explain the difference between malloc, calloc, realloc, and free.
3. Write a program that allocates memory for an array dynamically.
4. How does memory fragmentation affect dynamic allocation?
5. What are memory leaks, and how can you prevent them?
6. Describe how garbage values occur and how they are managed.
7. How does realloc work, and when should you use it?
8. Explain how memory is managed in a C program’s stack and heap.
9. Write a function to implement a simple dynamic array.
10. How would you debug memory issues in C?

Structures and Unions

1. How are structures allocated in memory?
2. Describe how unions work and when they should be used.
3. Write a program that uses a structure to store and display student information.
4. Explain how nested structures work.
5. What are the limitations of using unions?
6. How does padding affect memory in structures?
7. Write a program to demonstrate the use of bit fields within a structure.
8. What is a self-referential structure?
9. Describe the purpose of typedef with structures.
10. How can you use structures with dynamic memory allocation?

File I/O

1. Explain the different modes of opening a file in C.
2. How does fopen differ from freopen?
3. Write a program to read from a file and display its contents.
4. How can you write to a file in binary mode?
5. Describe the purpose of fseek and ftell.
6. How does buffered vs unbuffered I/O work in C?
7. What are EOF and NULL, and when are they used in file I/O?
8. Write a program to copy data from one file to another.
9. Explain how file pointers work.
10. How does the ferror function help with error handling in files?

Memory Management and Optimization

1. How does the operating system handle memory allocation for a program in C?
2. What is the difference between stack and heap memory, and how do they affect performance?
3. How can you detect and avoid memory leaks in C programs?
4. Explain memory fragmentation and how it can impact dynamic memory allocation.
5. What is the significance of memcpy() and memmove() in memory management?
6. How do you manage memory for large datasets without causing memory overflow or segmentation faults?
7. What is “buffer overflow,” and how can you prevent it in C programs?
8. Describe how dynamic memory is allocated and freed when dealing with multidimensional arrays.
9. How can memory alignment influence the performance of memory access in C programs?
10. How do memory pools and custom allocators work in C?