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.2Medium
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.3Medium
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.
Q.4Medium
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.5Medium
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.
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Q.6Medium
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.7Medium
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.8Medium
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.9Medium
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.10Medium
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++.
Q.11Medium
Analyze the memory leak in this code:
void func() {
int *p = malloc(100);
if(condition) return;
free(p);
}
Answer: B
When condition is true, the function returns without calling free(), causing a memory leak.
Q.12Medium
What is the output of this code?
int *p = calloc(3, sizeof(int));
printf("%d %d %d", p[0], p[1], p[2]);
Answer: B
calloc() initializes all allocated bytes to 0, so all integers are 0.
Q.13Medium
Consider reallocating memory:
int *p = malloc(10);
p = realloc(p, 20);
Answer: B
realloc() extends the existing allocation, preserving original data, and may return the same or different address.
Q.14Medium
Which allocation method is most suitable for a dynamically growing linked list?
Answer: B
Each node should be allocated individually with malloc() to allow dynamic growth and efficient memory usage.
Q.15Medium
How can you safely check if malloc() succeeded?
Answer: A
malloc() returns NULL (pointer value 0) on failure; always check before using the pointer.
Q.16Medium
In the context of dynamic memory, what does 'memory fragmentation' refer to?
Answer: A
Fragmentation occurs when memory is allocated and freed irregularly, leaving unused gaps that waste space.
Q.17Medium
What will happen if you try to allocate extremely large memory?
int *p = malloc(INT_MAX);
Answer: B
malloc() returns NULL if allocation fails (insufficient memory); always check the return value.
Q.18Medium
Which best practice prevents memory leaks in complex programs?
Answer: C
Disciplined memory management with matching alloc/free pairs and proper error handling prevents leaks.
Q.19Medium
What does realloc() do if the new size is smaller than the old size?
Answer: B
realloc() shrinks or expands memory. If new size is smaller, it reduces allocation and returns pointer to resized block.
Q.20Medium
What will be the output of this code?
int *p = (int*)malloc(5 * sizeof(int));
printf("%d", sizeof(p));
Answer: B
sizeof(p) returns the size of pointer itself (4 bytes on 32-bit, 8 bytes on 64-bit), not the allocated memory.
