text: #include <stdio.h>
  #include <string.h>
  
  int main(void) {
  	char *all = "안녕하세요";
  	char buf[16];
  	buf[0] = all[3];
  	buf[1] = all[4];
  	buf[2] = all[5];
  	buf[3] = '\0';
  	printf("%s\n", all);
  	printf("length= %d\n", strlen(all)); //5?
  	printf("all[3]= %c\n", all[3]);
  	printf("all[3][4][5]= %c%c%c\n", all[3], all[4], all[5]);
  	printf("buf = %s\n", buf);
  	return 0;
  }
  