What will be the output?
int arr[3][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
int *p = (int *)arr;
printf("%d", *(p+5));
Answer: B
Converting 2D array to int pointer treats it as 1D. p+5 points to the 6th element (0-indexed), which is 6.
Q.102Hard
What does realloc() do?
Answer: B
realloc() changes the size of previously allocated memory. It may return the same address or a new one depending on availability.
Q.103Hard
What is the primary use of const pointer (int * const p)?
Answer: B
int * const p is a constant pointer - the pointer address cannot be changed, but the value it points to can be modified.
Q.104Hard
Consider: int arr[] = {1,2,3,4,5}; int *p = arr + 2; What is arr - p?
Answer: A
arr points to arr[0], p points to arr[2]. arr - p = -2 (p is 2 positions ahead).
Q.105Hard
What is malloc(0) likely to return?
Answer: B
malloc(0) behavior is implementation-defined but typically returns a valid pointer. Freeing it is safe.
Advertisement
Q.106Hard
What will be printed?
int *p = (int*)malloc(5 * sizeof(int));
int *q = p;
p = NULL;
free(q);
Answer: C
q still holds the address even though p is NULL. free(q) properly deallocates memory.
Q.107Hard
What is the difference between arr and &arr if arr is an array?
int arr[5];
Answer: B
arr decays to pointer to first element (int*). &arr is pointer to whole array (int(*)[5]). Pointer arithmetic differs.
Q.108Hard
In pointer to function: int (*ptr)(int, int); What does this declare?
Answer: B
Parentheses around *ptr give pointer priority. It's a pointer to a function taking 2 ints and returning int.
Q.109Hard
What is the output of: printf("%p", NULL);?
Answer: C
%p prints pointer values. NULL representation depends on implementation, commonly shown as 0x0 or (nil).
Q.110Hard
For dynamic 2D array: int arr = (int)malloc(n * sizeof(int*)); What's missing?
Answer: B
This allocates row pointers only. Each row needs allocation: arr[i] = (int*)malloc(m * sizeof(int));
Q.111Hard
What is the relationship between arrays and pointers?
Answer: C
Array name acts as pointer to first element in expressions but they're distinct. &arr and arr differ in type.
Q.112Hard
Consider: const int *p; and int * const q; Which statement is true?
Answer: C
const int *p: pointer can change, data cannot. int * const q: pointer cannot change, data can be modified.
Q.113Hard
Which statement is true about nested structures in C?
Answer: B
C allows structures to have other structures as members. This is called nested structures and is a common practice.
Q.114Hard
What happens if you assign a union member and then access another member?
struct u { int a; char b; }; u.a = 257; printf("%d", u.b);
Answer: B
In a union, both members share memory. 257 in binary is 100000001. u.b (char) reads only the LSB, which is 1.
Q.115Hard
How can you initialize a structure array of 10 elements partially in C?
Answer: D
Both {0} and {} will initialize all members to zero. These are equivalent in C99 and later standards.
Q.116Hard
What is the difference between self-referential and recursive structures?
Answer: B
Self-referential structures contain pointers to the same structure type (like linked list nodes). Recursion refers to function calls, not structures.
Q.117Hard
Given union test { int x; char y[4]; }; If you set y[0]=65, y[1]=66, what happens to x?
Answer: C
Since union members share memory, setting y[0]=65 and y[1]=66 overwrites the int x value. The exact value depends on endianness.
Q.118Hard
Which approach is more memory efficient for storing 100 flags: array of char or bit fields in a structure?
Answer: B
Bit fields can pack 8 flags per byte, so 100 flags need ~13 bytes. Char array needs 100 bytes. Bit fields are more memory-efficient for flag storage.
Q.119Hard
In nested structures with pointers, which access method is correct? struct outer { struct inner *ptr; } *o; Accessing inner's member x:
Answer: D
Both o->ptr->x and (*o).ptr->x are equivalent. Arrow operator can chain for pointers, and (*pointer).member is equivalent to pointer->member.
Q.120Hard
What is the relationship between structure alignment and padding in modern C compilers?
Answer: B
Compilers add padding bytes between structure members to align them on boundaries (usually power of 2), improving memory access performance on the target architecture.
