Arrays & Strings
Consider the following code:
A
5
B
6
C
4
D
Undefined behavior
The string "HELLO" has 5 characters. The while loop counts characters until it encounters the null terminator '\0'. The output will be 5. The null terminator is not counted in the length.
For char arr[5] = {'a', 'b', 'c', 'd', 'e'}, is this a valid string?
A
Yes, always valid
B
No, missing null terminator
C
Only if last element is '\0'
D
Depends on compiler
Correct Answer:
B. No, missing null terminator
String functions expect null terminator. This array has no '\0', so it's a character array but NOT a proper string for str* functions.
What does the strspn() function do?
A
Finds substring in a string
B
Spans the initial segment containing only characters from specified set
C
Compares two strings
D
Reverses a string
Correct Answer:
B. Spans the initial segment containing only characters from specified set
strspn(str, charset) returns length of initial segment of str containing only characters from charset. Useful for token parsing.
What is the correct syntax to pass a 2D array to a function?
A
void func(int arr[][])
B
void func(int arr[3][4])
C
void func(int **arr)
D
Any of the above
Correct Answer:
B. void func(int arr[3][4])
First dimension can be omitted, but second must be specified: int arr[][4]. Option C (int **arr) is not equivalent - it's pointer to pointer.
In what scenario would you use memcpy() instead of strcpy()?
A
memcpy() is always faster
B
When copying binary data or strings without null terminators
C
When the destination is smaller
D
memcpy() is safer
Correct Answer:
B. When copying binary data or strings without null terminators
strcpy() assumes null-terminated strings. memcpy() copies exact number of bytes, suitable for binary data or embedded nulls.
What is the output of: char str[20]; scanf("%s", str); when input is 'Hello World'?
A
Entire 'Hello World' is stored
B
Only 'Hello' is stored (stops at whitespace)
C
Compilation error
D
Buffer overflow occurs
Correct Answer:
B. Only 'Hello' is stored (stops at whitespace)
%s format specifier stops reading at whitespace. To read entire line including spaces, use fgets() or %[^\n].
Which of the following correctly declares a pointer to an array (not array of pointers)?
A
int *arr[5];
B
int (*ptr)[5];
C
int [5]*ptr;
D
int &arr[5];
Correct Answer:
B. int (*ptr)[5];
Parentheses change precedence. int (*ptr)[5] is pointer to array of 5 ints. int *arr[5] is array of 5 pointers.
What will be the size in bytes of int arr[5] on a 32-bit system?
A
5 bytes
B
10 bytes
C
20 bytes
D
Depends on compiler
Correct Answer:
C. 20 bytes
On 32-bit systems, int is typically 4 bytes. 5 elements × 4 bytes = 20 bytes total.
In string handling, what is the difference between fgets() and gets()?
A
fgets() is slower
B
fgets() includes newline character, gets() doesn't
C
fgets() takes size parameter and is safer; gets() is unsafe (removed from C11)
D
gets() works only with integers
Correct Answer:
C. fgets() takes size parameter and is safer; gets() is unsafe (removed from C11)
gets() has no buffer overflow protection and was removed in C11. fgets(str, size, stdin) is the safer alternative with size limiting.
What is the output of: int arr[] = {10, 20, 30}; printf("%d", *(arr+1));?
A
10
B
20
C
30
D
Garbage value
arr+1 points to second element (arr[1]). Dereferencing gives value 20.
