Basic question about malloc

Hi, I'm looking for that whether the object allocated by malloc is the multiple of certain bytes! Or how does the malloc allocate dynamic memory ?? I does an experiment in my computer! #include<stdio.h> #include<stdlib.h> #define NUM 33 int main(int argc,const char *argv[]) { char *a, *b, *c; a = malloc(NUM); b = malloc(NUM); c = malloc(NUM); printf("a = %x\n",a); printf("b = %x\n",b); printf("c = %x\n",c); free(a); free(b); free(c); return 0; } But the result has no feature about a ,b ,c! Can someone tell me what's wrong with me? My GCC version is gcc (Debian 4.9.2-10) 4.9.2 mudongliang