Quiz for Dynamic memory allocation realloc

Q1: What is the primary purpose of realloc() in C?

A. To reallocate memory to a new size B. To allocate memory for the first time C. To free memory D. To initialize allocated memory with zeros

Q2: Which header file is required for realloc()?

A. stdio.h B. stdlib.h C. memory.h D. string.h

Q3: What happens if realloc() fails?

A. It returns NULL B. It frees the original block C. It terminates the program D. It returns garbage value

Q4: If the pointer passed to realloc() is NULL, what happens?

A. It behaves like malloc() B. It behaves like calloc() C. It causes an error D. It frees memory

Q5: If size is zero and ptr is not NULL in realloc(), what happens?

A. It behaves like free() B. It reallocates to zero size C. It keeps the same memory D. It gives segmentation fault

Q6: Which of the following is a safe way to use realloc()?

A. Assign directly to original pointer B. Assign to a temporary pointer first C. Ignore return value D. Call free() immediately after

Q7: What is preserved when realloc() changes the memory size?

A. All previous contents B. All previous contents up to new size C. Nothing D. Only first byte

Q8: If realloc() moves memory, what happens to the old block?

A. It is freed B. It becomes inaccessible but not freed C. It remains allocated D. It is overwritten

Q9: Which is the correct syntax for realloc()?

A. ptr = realloc(ptr, size); B. realloc(size, ptr); C. realloc(ptr); D. ptr = realloc(size);

Q10: If new size is larger, realloc() will:

A. Allocate new memory and copy old data B. Allocate new memory without copying C. Free old memory D. Crash the program

Q11: When should realloc() be used?

A. When increasing array size dynamically B. When creating arrays initially C. When freeing memory D. When copying strings

Q12: If realloc() returns NULL, what should be done?

A. Immediately free original pointer B. Use original pointer as it is C. Retry realloc() D. Ignore the error

Q13: What type of pointer does realloc() return?

A. void* B. char* C. int* D. depends on usage

Q14: Which of these is NOT true about realloc()?

A. It can increase memory size B. It can decrease memory size C. It always moves memory to new location D. It can free memory when size=0

Q15: If realloc() is called with size less than original size:

A. Extra memory is freed B. Extra memory remains unused C. Error occurs D. Garbage data appears

Q16: Can realloc() be used on memory allocated with calloc()?

A. Yes B. No C. Only sometimes D. Depends on compiler

Q17: What is the time complexity of realloc() in worst case?

A. O(1) B. O(n) C. O(log n) D. O(n^2)

Q18: What happens if pointer passed to realloc() was not allocated by malloc/calloc/realloc?

A. Undefined behavior B. It works fine C. It returns NULL safely D. It allocates new memory

Q19: Is it necessary to free memory returned by realloc()?

A. Yes B. No C. Only if size increased D. Only if moved

Q20: Which statement about realloc() is correct?

A. It can be used to shrink or grow allocated memory B. It only increases size C. It only decreases size D. It cannot free memory