Interview Prep | C
C Interview Questions

Top asked C interview questions for freshers and experienced developers. Practice and crack your next interview easily 🚀

Entry Mid Advanced
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• Entry Level

C Entry Level Q&A

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Q1. What is C language?
A. C is a general-purpose, procedural programming language used for system programming and application development.
Beginner
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Q2. What is a pointer?
A. A pointer is a variable that stores the memory address of another variable.
Beginner
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Q3. What is a variable?
A. A variable is a named storage location used to hold data.
Beginner
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Q4. What is a data type?
A. A data type defines the type of data a variable can hold like int, float, char.
Beginner
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Q5. What is a function?
A. A function is a block of code that performs a specific task.
Beginner
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Q6. Stack vs Heap?
A. Stack is used for static memory allocation, Heap is used for dynamic memory allocation.
Beginner
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Q7. What is malloc?
A. malloc() dynamically allocates memory but does not initialize it.
Beginner
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Q8. What is calloc?
A. calloc() allocates memory and initializes it to zero.
Beginner
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Q9. What is free()?
A. free() releases dynamically allocated memory.
Beginner
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Q10. What is NULL?
A. NULL represents a null pointer that does not point to any memory location.
Beginner
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Q11. What is a string in C?
A. A string is an array of characters ending with a null character \0.
Beginner
• Mid Level

C Mid Level Q&A

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Q1. What is a function prototype?
A. It declares the function before it is used.
Intermediate
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Q2. What is static keyword?
A. It retains variable value between function calls or restricts scope.
Intermediate
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Q3. What is const?
A. const makes a variable read-only.
Intermediate
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Q4. What is pointer arithmetic?
A. Operations performed on pointers like increment/decrement.
Intermediate
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Q5. What is double pointer?
A. Pointer to a pointer. Example: int **ptr.
Intermediate
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Q6. What is structure?
A. A structure groups variables of different types.
Intermediate
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Q7. What is union?
A. Union shares the same memory among all members.
Intermediate
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Q8. Difference between struct and union?
A. Struct allocates memory for all members, union shares memory.
Intermediate
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Q9. What is recursion?
A. A function calling itself.
Intermediate
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Q10. What is header file?
A. File containing function declarations. Example: stdio.h
Intermediate
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Q11. What is macro?
A. A macro is a preprocessor directive defined using #define.
Intermediate
• Advanced Level

C Advanced Level Q&A

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Q1. What is volatile?
A. Prevents compiler optimization for variables.
Advanced
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Q2. What is memory leak?
A. Memory allocated but not freed.
Advanced
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Q3. What is dangling pointer?
A. Pointer pointing to freed memory.
Advanced
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Q4. What is buffer overflow?
A. Writing beyond allocated memory.
Advanced
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Q5. What is segmentation fault?
A. Accessing invalid memory location.
Advanced
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Q6. What is function pointer?
A. Pointer that stores address of a function.
Advanced
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Q7. Difference between memcpy and memmove?
A. memcpy fails in overlap, memmove handles overlap safely.
Advanced
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Q8. What is inline function?
A. Function expanded at compile time.
Advanced
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Q9. What is typedef?
A. Used to create alias names for data types.
Advanced
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Q10. What is multi-threading in C?
A. Executing multiple threads using libraries like pthread.
Advanced
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Q11. What is strict aliasing?
A. Rules defining how pointers can access memory.
Advanced