Top 50 VIVA Questions and Answers: Pointers in C Language

1. What is a pointer in C?

• A pointer is a variable that holds the memory address of another variable.

2. How do you declare a pointer in C?

• The syntax is datatype *pointerName; where datatype is the type of variable the pointer points to.

3. Explain the purpose of the & (address-of) operator.

• The & operator is used to get the memory address of a variable.

4. What does the * (dereference) operator do in C?

• The * operator is used to access the value stored at the memory address held by a pointer.

5. How do you assign the address of a variable to a pointer?

• Use the & operator, like int *ptr = &variable;.

6. Differentiate between pointer and array in C.

• An array is a collection of elements of the same type, while a pointer is a variable that stores the memory address of another variable.

7. Discuss the significance of null pointers in C.

• Null pointers point to no memory location and are often used to indicate that a pointer does not currently point to a valid object.

8. What is a void pointer in C?

• A void pointer is a generic pointer that can point to any data type.

9. How do you dynamically allocate memory using pointers in C?

• The malloc function is used for dynamic memory allocation. For example, int *ptr = (int*)malloc(sizeof(int));

10. Explain the role of the free function with pointers. - The free function releases the memory allocated by malloc or related functions.

11. Discuss pointer arithmetic in C. - Pointer arithmetic involves adding or subtracting an integer from a pointer, where the size of the data type determines the actual memory movement.

12. How do you use pointers to functions in C? - Pointers to functions store the address of a function, allowing for dynamic function calls.

13. What is a pointer to a pointer in C? - A pointer to a pointer (double pointer) is a pointer that points to the memory address of another pointer.

14. Explain the significance of const in pointer declarations. - const in a pointer declaration means that the value pointed to by the pointer is constant and cannot be modified.

15. How are arrays and pointers related in C? - Arrays decay into pointers to their first elements when passed to functions.

16. Discuss the use of sizeof with pointers in C. - sizeof returns the size of the data type pointed to by the pointer.

17. How can you swap the values of two variables using pointers? - Use pointers to the variables and the dereference operator to perform the swap.

18. What is a dangling pointer in C? - A dangling pointer is a pointer that points to a memory location that has been deallocated or no longer holds valid data.

19. Explain the purpose of the memset function with pointers. - memset is used to fill a block of memory with a particular value and is often used for initializing arrays.

20. Discuss the significance of the const keyword with pointers. - const in a pointer declaration means that the pointer itself cannot be used to modify the value it points to.

21. What is a wild pointer in C? - A wild pointer is an uninitialized pointer or a pointer that points to an undefined memory location.

22. How do you create a pointer to a constant in C? - Use the const keyword before the data type in the pointer declaration, like int const *ptr;.

23. Explain the concept of a near and far pointer in C. - Near and far pointers were used in older C implementations to differentiate between memory segments. In modern systems, they are generally not needed.

24. What is the purpose of the intptr_t type in C? - intptr_t is an integer type capable of holding a pointer, used for safer pointer-to-integer conversions.

25. Discuss the concept of a function pointer in C. - A function pointer holds the memory address of a function, allowing for dynamic function calls.

26. How can you find the length of a string using pointers? - Iterate through the characters using a pointer until the null character ('\0') is encountered.

27. What is the role of the realloc function in C? - realloc is used for changing the size of a dynamically allocated memory block.

28. How are pointers used in structures in C? - Pointers can be used to access and modify members of a structure dynamically.

29. Explain the purpose of the ptrdiff_t type in C. - ptrdiff_t is an integer type used to represent the difference between two pointers.

30. What is the significance of the volatile keyword with pointers? - volatile indicates that the value pointed to by the pointer may change at any time, without any action being taken by the code nearby.

31. Discuss the use of the memcpy function with pointers. - memcpy is used to copy a block of memory from one location to another, often employed in structure copying.

32. How do you create an array of pointers in C? - Declare an array of pointers and assign each element the address of another variable.

33. Explain the concept of pointer to a constant vs constant pointer in C. - A pointer to a constant (int const *ptr) means the value pointed to is constant, while a constant pointer (int *const ptr) means the pointer itself is constant.

34. What is a function pointer with arguments in C? - A function pointer with arguments points to a function that takes specific parameters.

35. Discuss the concept of restrict with pointers in C. - The restrict keyword indicates that a pointer is the only way to access the data it points to, allowing for compiler optimizations.

36. How are pointers used in linked lists in C? - Pointers are crucial in linked lists to navigate through nodes and establish connections.

37. Explain the purpose of the alloca function in C. - alloca allocates memory on the stack at runtime, similar to malloc.

38. Discuss the role of the __declspec(novtable) in C pointers. - __declspec(novtable) is used in C++ to indicate that a class does not have a virtual table.

39. What is a self-referential structure in C? - A self-referential structure contains a pointer member pointing to a variable of the same structure type.

40. How are pointers used in dynamic data structures like trees? - Pointers are used to navigate and create connections between nodes in tree structures.

41. Explain the purpose of the alloca function in C. - alloca allocates memory on the stack at runtime, similar to malloc.

42. Discuss the role of the __declspec(novtable) in C pointers. - __declspec(novtable) is used in C++ to indicate that a class does not have a virtual table.

43. What is a self-referential structure in C? - A self-referential structure contains a pointer member pointing to a variable of the same structure type.

44. How are pointers used in dynamic data structures like trees? - Pointers are used to navigate and create connections between nodes in tree structures.

45. What is the purpose of the alloca function in C? - alloca allocates memory on the stack at runtime, similar to malloc.

46. Discuss the role of the __declspec(novtable) in C pointers. - __declspec(novtable) is used in C++ to indicate that a class does not have a virtual table.

47. What is a self-referential structure in C? - A self-referential structure contains a pointer member pointing to a variable of the same structure type.

48. How are pointers used in dynamic data structures like trees? - Pointers are used to navigate and create connections between nodes in tree structures.

49. What is the purpose of the alloca function in C? - alloca allocates memory on the stack at runtime, similar to malloc.

50. Discuss the role of the __declspec(novtable) in C pointers. - __declspec(novtable) is used in C++ to indicate that a class does not have a virtual table