Exercise 8.6 - Write calloc, by calling malloc

Question

The standard library function calloc(n,size) returns a pointer to n objects of size size, with the storage initialized to zero. Write calloc, by calling malloc or by modifying it.

/* The standard library function calloc(n,size) returns a pointer to n objects
/* if size size, with the storage intialized to zero. Write calloc,by callinng
/* malloc or modifying it */

/* calloc: allocate n objects of size size */

#include <stdio.h>
#include <stdlib.h>

void *mycalloc(unsigned, unsigned);

void *mycalloc(unsigned n, unsigned size) {
    unsigned i, nb;
    char *p, *q;

    nb = n * size;

    if ((p = q = malloc(nb)) != NULL)
        for (i = 0; i < nb; i++)
            *p++ = 0;
    return q;
}

int main(int argc, char *argv[]) {
    int *p = NULL;
    int i = 0;

    p = mycalloc(100, sizeof *p);
    if (NULL == p) {
        printf("mycalloc returned NULL");

    } else {
        for (i = 0; i <= 100; i++) {
            printf("%08X", p[i]);
            if (i % 8 == 7) {
                printf("\n");
            }
        }
        printf("\n");
        free(p);
    }
    return 0;
}

Explanation