Header File 

alloc.h, stdlib.h 

Category 

Memory Routines 

Prototype 

void *calloc(size_t nitems, size_t size); 

Description 

Allocates main memory. 

calloc provides access to the C memory heap. The heap is available for dynamic allocation of variable-sized blocks of memory. Many data structures, such as trees and lists, naturally employ heap memory allocation. 

calloc allocates a block of size nitems * size. The block is initialized to 0. 

Return Value 

calloc returns a pointer to the newly allocated block. If not enough space exists for the new block or if nitems or size is 0, calloc returns NULL. 

Example  

 #include <stdio.h>
 #include <alloc.h>
 #include <string.h>
 int main(void)
 {
    char *str = NULL;
    /* allocate memory for string */
    str = (char *) calloc(10, sizeof(char));
    /* copy "Hello" into string */
    strcpy(str, "Hello");
    /* display string */
    printf("String is %s\n", str);
    /* free memory */
    free(str);
    return 0;
 }

Portability