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

int main() {
char *pStr = "123456";
char tmp[3] = {};

int i=0;
do {
memcpy(tmp, (pStr+i), 2);
printf("%s\n", tmp);
i+=2;
}
while (*(pStr+i+1) != '\0');
}