The ones who are crazy enough to think they can change the world are the ones who do.
- Steve Jobs

C Calloc()

Why Calloc?

Now it's time to partition the microprocessor's memory to your 6 teams of your startup company, If you want to allocate non-consecutive memory location to every team, then calloc() will help you out there.

calloc in c

What is Calloc?

  • calloc() is the programmer's shorthand to represent clear allocation.
  • calloc() allocates a block of size bytes to a program from the heap.
  • calloc() allocate an exact quantity of memory explicitly to a program, when required.
  • allocation of memory is done in non-consecutive memory location.

Calloc() Syntax

Syntax 
void *calloc  (size_t nitems, size_t size);

calloc() vs malloc()

Type calloc() malloc()
Number of argruments 2 1
Block Initialization 0 some garbage value
say 2563547
Return value (success) malloc() returns a pointer to the newly allocated block of memory calloc() returns a pointer to the newly allocated block of memory
Return value (failure) malloc() returns NULL calloc() returns NULL
syntax void *calloc (size_t nitems, size_t size); void *malloc (size_t size);

C Program - Using Calloc()

From the following program we will prove that a memory blocks which are allocated by using calloc() will be represented by a value zero in it.

calloc-1.c 
#include <stdio.h>
#include <stdlib.h>
int main()
{
int *numbers = (int*)calloc(4, sizeof(int));
int i;
numbers[0] = 1;
numbers[1] = 2;
numbers[2] = 3;
printf("\nStored integers are ");
for(i = 0; i < 4; i++)
printf("\nnumbers[%d] = %d ", i, numbers[i]);
return 0;
}
  • numbers[0] = 1
  • numbers[1] = 2
  • numbers[2] = 3
  • numbers[3] = 0

Note:

Check numbers[3] in the above output, clearly calloc() initializes the allocated block to 0's.

Same C program - using malloc().

Let's do the same program using malloc() function to prove that a memory blocks which are allocated by using malloc() will be represented by some garbage value in it.

calloc-2.c 
#include <stdio.h>
#include <stdlib.h>
int main()
{
int *numbers = (int*)malloc(4* sizeof(int));
int i;
numbers[0] = 1;
numbers[1] = 2;
numbers[2] = 3;
printf("\nStored integers are ");
for(i = 0; i < 4; i++)
printf("\nnumbers[%d] = %d ", i, numbers[i]);
return 0;
}
  • numbers[0] = 1
  • numbers[1] = 2
  • numbers[2] = 3
  • numbers[3] = 1549890657

Note:

Check numbers[3] in the above output, clearly malloc() initializes the allocated block to some garbage value.

Did You Know?

malloc() leads to a security risk because its unpredictable whether the block of memory is allocated or not, as it represent every individual allocated block with some garbage value whereas calloc() represents by zero.

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