怎么将一个十进制数转化为二进制数并打印出来

#define _CRT_SECURE_NO_WARNINGS 1 #include<stdio.h> #include<stdlib.h> int main() { int i = 0; int j = 0; int num = 0; int arr[100]; int k = 0; scanf("%d", &num); while (num !=0 )//取余动作，直至余数为0 { arr[k]=num % 2; num = num / 2; k++; } i = k; for (k = i - 1; k >= 0;k--)//反向输出二进制数 { printf("%d", arr[k]); } system("pause"); return 0; }