calloc 2

 //calloc

#include <stdio.h>

#include <stdlib.h> 

int main() {

    int *ptr;

    int n = 5;

    printf("Enter number of values:\n");

    scanf("%d",&n);

    

    ptr = (int *)calloc(n, sizeof(int));

    if (ptr == NULL) {

        printf("Memory allocation failed!\n");

        return 1; 

    }

   

    printf("\n");

   

    for (int i = 0; i < n; i++) {

        ptr[i] = i *10+10;

    }

    printf("After assigning values:\n");

    for (int i = 0; i < n; i++) {

        printf("%d ", ptr[i]); 

    }

    printf("\n");

   

    free(ptr);

    ptr = NULL; 

    return 0;

}

i

Output

After assigning values:
10 20 30 40 50

---

🟦 Step 9: Free the Allocated Memory

free(ptr);

Explanation

The free() function releases the dynamically allocated memory.

Before free():

ptr
 ↓

+-----+-----+-----+-----+-----+
| 10  | 20  | 30  | 40  | 50  |
+-----+-----+-----+-----+-----+

After free():

Memory Released to the Operating System

The memory is no longer available for use.

---

🟦 Step 10: Assign NULL to the Pointer

ptr = NULL;

Why?

After calling free(), the pointer still contains the old memory address.

Such a pointer is called a dangling pointer.

Assigning NULL makes the pointer safe.

Before

ptr

↓

0x7ffab120

After

ptr

↓

NULL

---

📊 Program Flow Diagram

Start
   │
   ▼
Read n
   │
   ▼
Allocate Memory using calloc()
   │
   ▼
Is ptr == NULL?
   │
 ┌─┴───────────────┐
 │                 │
Yes               No
 │                 │
 ▼                 ▼
Print Error     Store Values
Exit               │
                   ▼
             Print Values
                   │
                   ▼
              Free Memory
                   │
                   ▼
              ptr = NULL
                   │
                   ▼
                  End

---

🖥 Sample Execution

Input

Enter number of values:
5

Output

After assigning values:
10 20 30 40 50

---

📦 Memory Representation

Before Allocation

ptr

↓

NULL

---

After calloc()

ptr

↓

+----+----+----+----+----+
| 0  | 0  | 0  | 0  | 0  |
+----+----+----+----+----+

---

After Storing Values

ptr

↓

+----+----+----+----+----+
|10  |20  |30  |40  |50  |
+----+----+----+----+----+

---

After free()

Memory Released

ptr

↓

NULL

---

🌟 Advantages of calloc()

• ✅ Allocates memory dynamically during program execution.
• ✅ Initializes all allocated memory to 0.
• ✅ Helps avoid using uninitialized data.
• ✅ Suitable when the number of elements is known only at runtime.

---

⚠ Precautions

• Always check whether calloc() returns NULL.
• Always access elements within the allocated range (0 to n-1).
• Always call free() when the memory is no longer needed.
• Set the pointer to NULL after free() to avoid dangling pointers.