4.3.1 - Introduction to Strings and its Functions ( Strcat(),Strlen(),Strcmp() etc).

1. What does the null character "\0" represent in a string in C?

(A) The first character of the string
(B) The end of the string
(C) A whitespace character
(D) A separator

Correct Answer: (B) The end of the string

2. Which function is used to find the length of a string in C?

(A) strlen()
(B) strcpy()
(C) strcat()
(D) strcmp()

Correct Answer: (A) strlen()

3. What is the return value of the strlen() function when applied to an empty string?

(A) -1
(B) 1
(C) 0
(D) Undefined

Correct Answer: (C) 0

4. Which function is used to copy one string to another in C?

(A) strcat()
(B) strcpy()
(C) strlen()
(D) strcmp()

Correct Answer: (B) strcpy()

5. Which function is used to concatenate two strings in C?

(A) strcpy()
(B) strcmp()
(C) strcat()
(D) strlen()

Correct Answer: (C) strcat()

6. What is the return value of strcmp() if two strings are identical?

(A) 0
(B) 1
(C) -1
(D) Undefined

Correct Answer: (A) 0

7. Which header file is required for using string functions like strlen(), strcpy(), and strcmp()?

(A) stdio.h
(B) stdlib.h
(C) string.h
(D) conio.h

Correct Answer: (C) string.h

8. If char s1[] = "hello"; and char s2[] = "world";, what does strcat(s1, s2); do?

(A) Combines the two strings and stores them in s2
(B) Combines the two strings and stores them in s1
(C) Compares the two strings
(D) Finds the length of the strings

Correct Answer: (B) Combines the two strings and stores them in s1

9. Which of the following string functions compares two strings lexicographically?

(A) strcpy()
(B) strcat()
(C) strcmp()
(D) strlen()

Correct Answer: (C) strcmp()

10. If char s1[] = "abc"; and char s2[] = "ABC";, what does strcmp(s1, s2); return?

(A) 0
(B) Positive integer
(C) Negative integer
(D) Undefined

Correct Answer: (C) Negative integer

11. Which function can be used to safely copy a specified number of characters from one string to another?

(A) strncpy()
(B) strncat()
(C) strncmp()
(D) strrev()

Correct Answer: (A) strncpy()

12. What does the strcmp() function return if the first string is lexicographically smaller than the second?

(A) 0
(B) 1
(C) -1
(D) A negative integer

Correct Answer: (D) A negative integer

13. What will strlen("hello world") return?

(A) 10
(B) 11
(C) 12
(D) 9

Correct Answer: (B) 11

14. Which of the following strings will be stored correctly in memory?

(A) "abc"
(B) "abc\0"
(C) 'abc'
(D) Both (A) and (B)

Correct Answer: (D) Both (A) and (B)

15. Which function can be used to append a specific number of characters from one string to another?

(A) strncat()
(B) strcat()
(C) strncpy()
(D) strncmp()

Correct Answer: (A) strncat()

16. What does strcpy() do with the null terminator \0 when copying a string?

(A) Ignores it
(B) Copies it
(C) Replaces it
(D) Appends it at the start

Correct Answer: (B) Copies it

17. What is the output of strcmp("apple", "banana")?

(A) 0
(B) Positive integer
(C) Negative integer
(D) Undefined

Correct Answer: (C) Negative integer

18. In C, strings are stored as arrays of characters terminated by which character?

(A) NULL
(B) '\0'
(C) ' ' (space)
(D) EOF

Correct Answer: (B) '\0'

19. Which of the following functions is not used for string comparison?

(A) strcmp()
(B) strncmp()
(C) strcpy()
(D) Both (A) and (B)

Correct Answer: (C) strcpy()

20. What will the function strcmp("apple", "apple") return?

(A) 1
(B) -1
(C) 0
(D) Undefined

Correct Answer: (C) 0

4.3.2 - String Handling Functions.

21. Which function is used for string concatenation in C?

(A) strcpy()
(B) strcat()
(C) strcmp()
(D) strlen()

Correct Answer: (B) strcat()

22. What does the strcat() function do?

(A) Copies one string into another
(B) Compares two strings
(C) Appends one string to another
(D) Finds the length of the string

Correct Answer: (C) Appends one string to another

23. What is the correct syntax of the strcat() function?

(A) int strcat(char* dest, char* src)
(B) char* strcat(char* dest, const char* src)
(C) char* strcat(const char* dest, char* src)
(D) int strcat(const char* dest, const char* src)

Correct Answer: (B) char* strcat(char* dest, const char* src)

24. What will strlen("Hello World") return?

(A) 11
(B) 10
(C) 12
(D) 9

Correct Answer: (A) 11

25. Which header file is needed for string functions like strcpy() and strlen()?

(A) stdlib.h
(B) conio.h
(C) string.h
(D) math.h

Correct Answer: (C) string.h

26. Which function is used to copy one string to another in C?

(A) strcpy()
(B) strcat()
(C) strcmp()
(D) strlen()

Correct Answer: (A) strcpy()

27. Which function is used to determine the length of a string in C?

(A) strcpy()
(B) strcmp()
(C) strlen()
(D) strcat()

Correct Answer: (C) strlen()

28. In strcat(), the source string is:

(A) Overwritten
(B) Appended to the destination string
(C) Compared with the destination string
(D) Copied before appending

Correct Answer: (B) Appended to the destination string

29. What does the strlen() function return?

(A) Length of the string including the null character
(B) Length of the string excluding the null character
(C) Always 0
(D) Undefined

Correct Answer: (B) Length of the string excluding the null character

30. If char str[] = "C language";, what will strlen(str) return?

(A) 9
(B) 10
(C) 11
(D) 12

Correct Answer: (C) 11

31. What is the output of strcpy(dest, src) if dest has a size smaller than src?

(A) Copies partially
(B) Causes undefined behavior
(C) Copies completely
(D) Returns error

Correct Answer: (B) Causes undefined behavior

32. Which function compares two strings lexicographically?

(A) strcat()
(B) strcpy()
(C) strcmp()
(D) strlen()

Correct Answer: (C) strcmp()

33. What does strcmp() return if the first string is lexicographically smaller than the second?

(A) A positive integer
(B) 0
(C) A negative integer
(D) Undefined behavior

Correct Answer: (C) A negative integer

34. What will strlen("") return?

(A) -1
(B) 1
(C) 0
(D) Undefined

Correct Answer: (C) 0

35. Which string function returns the concatenated string?

(A) strcpy()
(B) strlen()
(C) strcat()
(D) strcmp()

Correct Answer: (C) strcat()

36. What does strcpy(dest, src) do?

(A) Compares src and dest
(B) Copies src to dest
(C) Appends src to dest
(D) Returns the length of src

Correct Answer: (B) Copies src to dest

37. If char s[] = "apple";, what will strlen(s) return?

(A) 4
(B) 5
(C) 6
(D) 0

Correct Answer: (B) 5

38. What will be the result of strcmp("apple", "apple")?

(A) 0
(B) 1
(C) -1
(D) Undefined

Correct Answer: (A) 0

39. Which function is used to concatenate two strings in C?

(A) strcpy()
(B) strcat()
(C) strlen()
(D) strcmp()

Correct Answer: (B) strcat()

40. What happens if strcmp() finds two identical strings?

(A) Returns a positive integer
(B) Returns a negative integer
(C) Returns 0
(D) Causes an error

Correct Answer: (C) Returns 0

4.3.3 - String Pointers.

41. What does a pointer store in C?

(A) Value of a variable
(B) Address of a variable
(C) Size of a variable
(D) Type of a variable

Correct Answer: (B) Address of a variable

42. What is the primary use of pointers in C?

(A) To store values directly
(B) To store memory addresses
(C) To store array indexes
(D) To declare variables

Correct Answer: (B) To store memory addresses

43. What does the * symbol represent in pointer declaration?

(A) Value of the pointer
(B) Memory address
(C) Dereferencing the pointer
(D) Array indexing

Correct Answer: (C) Dereferencing the pointer

44. How do you declare a pointer to a string in C?

(A) char *ptr;
(B) int *ptr;
(C) float *ptr;
(D) double *ptr;

Correct Answer: (A) char *ptr;

45. What will char *ptr = "Hello"; store in ptr?

(A) The string "Hello"
(B) The first character of the string
(C) The address of the string
(D) A null value

Correct Answer: (C) The address of the string

46. Which of the following is true about pointers and arrays?

(A) Pointers and arrays are the same
(B) Arrays store addresses, pointers store values
(C) Arrays store values, pointers store addresses
(D) Pointers can’t access arrays

Correct Answer: (C) Arrays store values, pointers store addresses

47. How do you access the value of a variable through a pointer?

(A) By using &ptr
(B) By using *ptr
(C) By using ptr++
(D) By using ptr--

Correct Answer: (B) By using *ptr

48. What will *(ptr + 2) access in a string pointer ptr pointing to "Hello"?

(A) First character
(B) Second character
(C) Third character
(D) Null character

Correct Answer: (C) Third character

49. How can you move to the next character in a string using a pointer?

(A) ptr++
(B) ptr--
(C) *ptr + 1
(D) *ptr++

Correct Answer: (A) ptr++

50. Which of the following function uses pointers to pass variables by reference?

(A) strcat()
(B) scanf()
(C) printf()
(D) malloc()

Correct Answer: (B) scanf()

51. How does char *ptr = str; work in C?

(A) Assigns the first character of str to ptr
(B) Assigns the address of str to ptr
(C) Copies str to ptr
(D) Converts str to ptr

Correct Answer: (B) Assigns the address of str to ptr

52. What is the output of the following code?

            char str[6] = "Hello";
            char *ptr = str;
            printf("%c", *(ptr+1));

(A) H
(B) e
(C) l
(D) o

Correct Answer: (B) e

53. What does the expression ptr[2] mean if ptr is a pointer to a string?

(A) Pointer addition
(B) Pointer subtraction
(C) Accesses the third character of the string
(D) Multiplies the pointer value by 2

Correct Answer: (C) Accesses the third character of the string

54. What does char *ptr = "Hello"; do in memory?

(A) Copies "Hello" to ptr
(B) Points ptr to the address of "Hello"
(C) Initializes ptr with an empty string
(D) Assigns a null value to ptr

Correct Answer: (B) Points ptr to the address of "Hello"

55. Which operator is used to get the address of a variable in C?

(A) *
(B) &
(C) +
(D) -

Correct Answer: (B) &

56. What is the output of this code?

            char str[6] = "World";
            char *ptr = str;
            while(*ptr != '\0') {
                printf("%c", *ptr);
                ptr++;
            }

(A) World
(B) orld
(C) Worl
(D) Nothing

Correct Answer: (A) World

57. Which function can dynamically allocate memory for a string?

(A) malloc()
(B) free()
(C) sizeof()
(D) realloc()

Correct Answer: (A) malloc()

58. Which of the following is true about pointer arithmetic in C?

(A) ptr++ increments the pointer to point to the next element
(B) ptr++ decrements the pointer to point to the previous element
(C) Pointers cannot be incremented
(D) Pointers can only be decremented

Correct Answer: (A) ptr++ increments the pointer to point to the next element

59. What does *(ptr++) do?

(A) Increments the value of the pointer
(B) Moves the pointer to the next memory location after dereferencing
(C) Decrements the pointer
(D) Causes a segmentation fault

Correct Answer: (B) Moves the pointer to the next memory location after dereferencing

60. Why is it necessary to use free() with dynamically allocated memory?

(A) To prevent memory leakage
(B) To increase memory allocation
(C) To avoid pointer arithmetic errors
(D) To initialize variables

Correct Answer: (A) To prevent memory leakage