Interview Questions on Chapter 5: Arrays and Strings

Here are 30 interview questions along with their answers on Chapter 5: Arrays and Strings:

Chapter 5: Arrays and Strings

1. What is an array in C?

• Answer: An array in C is a collection of elements of the same type, stored in contiguous memory locations. The elements can be accessed using an index.

2. How do you declare an array in C?

• Answer: You declare an array in C by specifying the data type, followed by the array name, and the number of elements:
  c int arr[10];

3. What is the difference between a one-dimensional and a two-dimensional array?

• Answer:
  • A one-dimensional array is a linear list of elements.
  • A two-dimensional array is an array of arrays, where each element is itself an array.
    c int arr[5]; // One-dimensional int arr[5][5]; // Two-dimensional

4. How do you access elements of an array?

• Answer: You can access array elements using the index, starting from 0. For example:
  c int arr[5] = {1, 2, 3, 4, 5}; printf("%d", arr[2]); // Output: 3

5. What are multi-dimensional arrays?

• Answer: Multi-dimensional arrays are arrays that have more than one index. The most common is the two-dimensional array (like a matrix), but arrays can have more dimensions (e.g., 3D arrays).

6. Can arrays in C store elements of different data types?

• Answer: No, arrays in C can only store elements of the same data type. To store different data types, structures or unions should be used.

7. What is a pointer to an array in C?

• Answer: A pointer to an array is a pointer that holds the address of the first element of an array.
  c int arr[5] = {1, 2, 3, 4, 5}; int *ptr = arr; // ptr points to the first element of arr

8. What is the syntax for declaring and initializing an array in C?

• Answer:
  c int arr[5] = {1, 2, 3, 4, 5}; // Declaration and initialization

9. How do you initialize a one-dimensional array?

• Answer: You can initialize a one-dimensional array at the time of declaration:
  c int arr[] = {1, 2, 3, 4, 5};

10. How do you pass an array to a function?

• Answer: In C, arrays are passed to functions by reference, meaning the function receives the address of the first element of the array.
  c void display(int arr[], int size) { for (int i = 0; i < size; i++) { printf("%d ", arr[i]); } }

11. What is a string in C?

• Answer: A string in C is a sequence of characters stored in an array, terminated by a null character ('\0').

12. How do you declare a string in C?

• Answer: A string is declared as an array of characters:
  c char str[20] = "Hello";

13. How do you find the length of a string in C?

• Answer: You can find the length of a string using the strlen() function, which returns the number of characters excluding the null terminator.
  c int len = strlen(str);

14. What is the use of the strcpy() function in C?

• Answer: The strcpy() function is used to copy one string to another:
  c strcpy(dest, src);

15. What is the difference between strcpy() and strncpy()?

• Answer:
  • strcpy() copies a string until it reaches the null terminator.
  • strncpy() copies at most the specified number of characters, ensuring the destination string is null-terminated.

16. What is the strcmp() function used for?

• Answer: The strcmp() function compares two strings lexicographically and returns:
  • 0 if they are equal,
  • A negative value if the first string is lexicographically smaller,
  • A positive value if the first string is larger.

17. How do you concatenate two strings in C?

• Answer: The strcat() function is used to concatenate two strings.
  c strcat(str1, str2);

18. What is the difference between scanf() and gets() for reading strings?

• Answer:
  • scanf() reads input and stops at the first whitespace (space, tab, or newline).
  • gets() reads an entire line of input, including spaces, but is dangerous as it doesn’t check for buffer overflow.

19. What is the size of a string in C?

• Answer: The size of a string in C is determined by the number of characters in the string, including the null terminator '\0'.

20. What is the null character \0 in a string?

• Answer: The null character \0 marks the end of a string in C. It indicates that the string has no more characters.

21. How do you reverse a string in C?

• Answer: You can reverse a string by swapping its characters from the beginning and the end until the middle:
  c void reverse(char str[]) { int start = 0, end = strlen(str) - 1; while (start < end) { char temp = str[start]; str[start] = str[end]; str[end] = temp; start++; end--; } }

22. What is the use of the memset() function?

• Answer: The memset() function sets a specified number of bytes in a block of memory to a given value. It’s commonly used to initialize arrays.
  c memset(arr, 0, sizeof(arr));

23. What are the limitations of arrays in C?

• Answer: Arrays in C have a fixed size and cannot be resized once allocated. Also, they do not have bounds checking, so accessing out-of-bounds elements can lead to undefined behavior.

24. What is a dynamic array in C?

• Answer: A dynamic array is an array whose size can be determined at runtime using functions like malloc() or calloc() for memory allocation.

25. What is the difference between malloc() and calloc()?

• Answer:
  • malloc() allocates a block of memory without initializing it.
  • calloc() allocates memory and initializes all bytes to zero.

26. How can you access individual characters in a string?

• Answer: You can access individual characters in a string using array indexing:
  c char str[] = "Hello"; printf("%c", str[1]); // Output: e

27. What is the strstr() function?

• Answer: The strstr() function searches for the first occurrence of a substring in a string and returns a pointer to it.
  c char *substr = strstr(str, "ell");

28. Can you pass a string to a function in C?

• Answer: Yes, strings are passed to functions by reference, meaning the function receives the address of the first character of the string.

29. What is a string literal in C?

• Answer: A string literal is a sequence of characters enclosed in double quotes. It is automatically null-terminated:
  c char str[] = "Hello";

30. What is the difference between a string array and a character array in C?

• Answer:
  • A string array is an array of characters terminated by '\0' (a string).
  • A character array is a general array of characters that may or may not form a valid string.

These questions and answers cover the fundamentals of arrays and strings in C, including how to work with them, common functions, and their limitations.