calloc() takes two arguments (number of elements and size) and initializes all allocated bytes to zero, unlike malloc().
Q.782Medium
What will be the output of the following code?
int *ptr = malloc(sizeof(int));
if(ptr == NULL) printf("Failed");
else printf("Success");
Answer: B
In typical scenarios, malloc() successfully allocates memory and returns non-NULL pointer, printing 'Success'. NULL check is good practice for error handling.
Q.783Easy
Which function is used to free dynamically allocated memory?
Answer: C
free() is the standard function to deallocate memory previously allocated by malloc(), calloc(), or realloc().
Q.784Medium
What is a memory leak in C?
Answer: B
A memory leak occurs when allocated memory is not freed, consuming system resources without releasing them back.
Q.785Medium
What happens when you try to access memory after calling free()?
Answer: B
Accessing freed memory results in undefined behavior and is a critical bug. The memory may be reallocated for other purposes.
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Q.786Medium
What is the purpose of realloc() function?
Answer: B
realloc() resizes a previously allocated memory block. It can increase or decrease the size and preserves existing data.
Q.787Medium
Which of the following is correct for dynamic array allocation?
Answer: B
Dynamic array allocation requires pointer and malloc() with proper size calculation. VLAs are not standard C.
Q.788Medium
What is double free error?
Answer: B
Double free error occurs when free() is called on the same memory block twice, causing undefined behavior and program crash.
Q.789Medium
Analyze this code:
char *str = malloc(5);
strcpy(str, "Hello");
How many bytes should malloc allocate for safety?
Answer: B
String "Hello" has 5 characters plus 1 null terminator (\0), requiring 6 bytes total.
Q.790Medium
What is the output?
int *p = malloc(sizeof(int) * 3);
p[0] = 1; p[1] = 2; p[2] = 3;
printf("%d", *(p+2));
Answer: C
*(p+2) is equivalent to p[2], which contains 3. Pointer arithmetic works with dynamic arrays.
Q.791Hard
What will happen if malloc() fails and returns NULL but code doesn't check?
Answer: B
Dereferencing a NULL pointer causes undefined behavior, typically resulting in segmentation fault or program crash.
Q.792Hard
Which statement about dynamic memory is TRUE?
Answer: B
Dynamic memory persists until free() is called, unlike automatic variables which are freed at function end.
Q.793Hard
What is the issue in this code?
void func() {
int *p = malloc(sizeof(int));
*p = 5;
}
int main() {
func();
// p is not accessible here
return 0;
}
Answer: B
The pointer p is local to func(). Memory is allocated but never freed, causing a memory leak.
Q.794Hard
What is the correct way to allocate memory for 2D dynamic array (3x4)?
Answer: B
For true 2D dynamic array, allocate pointer array first, then allocate each row. Option C is 1D linear allocation.
Q.795Hard
What does this realloc() call do?
int *p = malloc(5 * sizeof(int));
p = realloc(p, 10 * sizeof(int));
Answer: B
realloc() resizes the memory block while preserving existing data. If expansion in-place fails, it allocates new block and copies data.
Q.796Easy
How much memory is allocated by malloc(sizeof(int) * 10) on a 32-bit system where sizeof(int) = 4?
Answer: B
sizeof(int) * 10 = 4 * 10 = 40 bytes on a 32-bit system.
Q.797Easy
Which header file must be included to use malloc(), calloc(), and free() functions?
Answer: B
All memory allocation and deallocation functions are declared in <stdlib.h>.
Q.798Easy
What is the key difference between malloc() and calloc()?
Answer: B
calloc() takes two parameters (count, size) and initializes memory to 0, while malloc() takes one parameter and leaves memory uninitialized.
Q.799Medium
Which of the following correctly allocates memory for an array of 5 strings (each max 20 characters)?
Answer: D
Option B uses dynamic allocation (2D array), Option C uses static allocation. Both are valid but for different scenarios.
Q.800Medium
What is the purpose of typecasting in malloc()?
int *p = (int*)malloc(sizeof(int));
Answer: C
Typecasting malloc() is optional in C but improves readability. It's mandatory in C++.
