ELEVATE SKILLS!
Q: 1 What is the output of following program?
#include<stdio.h>
#include<stdlib.h>
void main()
{
char *ptr=(char*)calloc(100,1);
ptr="Suraku Academy";
printf("%s",ptr);
}
Suraku
Suraku Academy
Address of ptr
Compile Time Error
[ Option B ]
Here first memory is allocated dynamically using calloc(100,1) and the returned address is stored in the pointer ptr.
However, in the next statement, ptr = "Suraku Academy"; the pointer is reassigned to point to a string literal instead of the allocated memory. This means the previously allocated memory becomes unused, but the pointer now correctly points to the string "Suraku Academy".
When printf("%s",ptr); is executed, it prints the string stored at the address pointed to by ptr, which is "Suraku Academy".
Q: 2 What is the problem with following code?
#include<stdio.h>
int main()
{
int *ptr = (int *)malloc(sizeof(int));
ptr=NULL;
free(ptr);
}
Memory Leak.
Compile Time Error.
Dangling Pointer.
Wild Pointer.
[ Option A ]
In the given code, memory is dynamically allocated using malloc() and its address is stored in the pointer ptr. Immediately after allocation, the pointer is set to NULL using ptr=NULL;. This causes the original memory address returned by malloc() to be lost, meaning there is no way to access or free that allocated memory anymore.
As a result, the allocated memory remains unused and cannot be reclaimed, which leads to a Memory Leak.
Calling free(ptr) after setting ptr to NULL has no effect, because freeing a NULL pointer is safe but does nothing.
Q: 3 What is the return type of malloc() function?
void*
int*
Pointer of allocated memory type
Depends on compiler
[ Option A ]
In C, the malloc() function returns a pointer of type void*, which represents a generic pointer to the allocated memory block. This pointer can be typecast to any data type pointer as required.
| DMA FUNCTION | DESCRIPTION | RETURN TYPE |
|---|---|---|
| malloc() | Allocates a single block of memory and uninitialized. | void* |
| calloc() | Allocates multiple blocks and initializes to zero. | void* |
| realloc() | Resizes previously allocated memory. May return a new address. | void* |
| free() | Deallocates allocated memory. Does not return any value. | void |
Q: 4 Which function is used to delete the allocated memory space?
delete();
free();
dealloc();
remove();
[ Option B ]
In C, the free() function used to deallocate dynamically allocated memory. It releases the memory that was previously allocated using malloc(), calloc(), or realloc(), making it available for future use.
Q: 5 What is the output of the below code?
void main()
{
int *ptr;
ptr=(int *)calloc(1,sizeof(int));
*ptr=101;
printf("%d",*ptr);
}
10
0
101
5
[ Option C ]
Here, memory for one integer is allocated dynamically using calloc(1, sizeof(int)). Although calloc() initializes the allocated memory to zero, the next statement assigns the value 101 to the allocated memory using *ptr = 101;.
Therefore, when printf("%d",*ptr); is executed, it prints the value stored at that memory location, which is 101.
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