How to write a program Convert Numbers to Binary in C

Here is my very basic my approach to this problem. This program converts numbers to binary in C using simple basic C concepts. I guess this problem is supposed to teach how to work around a limitation/quirk when programming, and basically encourages to think a bit differently.

#include<stdio.h>

int main(void) {
    int input,binary=0,x;

//Take and see if input is a positive number
    do {
        printf("Please enter POSITIVE a number:");
        scanf("%d",&input);}
    while(input<0);

    x=input;

//Convert to binary
//Using 0 causes problems, so using 9 instead of 0
    while(x!=0)
    {
        binary=binary*10;
        if(x%2==1){
        binary=binary+1;
        }
        if(x%2==0){
        binary=binary+9;
        }

        x=x/2;
    }

//Its in binary but its reversed
//The 0s are in 0 we need to fix that as well
//reverse and replace here
int temp=binary,reverse=0,y;
    while(temp!=0)
    {
        y=temp%10;
        if(y==9){y=0;}
        reverse=(reverse*10)+y;
        temp=temp/10;
    }


//Print the result
    printf("\n\t\t\t%d",reverse);

    return 0;
}

Gist at https://gist.github.com/SohanChy/bff3490f203b91c5284e