How do I properly declare this variable?

I am trying to write a program in C that takes a positive integer that is input and then counts down to zero and back up to the number by 1. I am getting errors when trying to run the code saying that my variables usernum and usernum2 are undeclared. In the main function I declare them both as integers so what am I doing wrong?

#include <stdio.h>

`
void loop_down_to_zero(){
    while (usernum2 >= 0){
       printf("%d\n", &usernum2);
       usernum2--;
       if (usernum2 ==0) {
          printf("****\n");
       }
    }
}
void loop_up_to_zero(){
    while (usernum2 < usernum){
       usernum2++;
       printf("%d\n", usernum2);
    }
}

int main(int argc, char * argv[]) {
   int usernum;
   int usernum2;
   usernum2 = usernum;
   printf("Enter a positive integer: \n");
   scanf("%d", &usernum);
   while (usernum <= 0){
      printf("Error, enter a positive integer: \n");
      scanf("%d", &usernum);
   }
   if (usernum > 0) {
      loop_down_to_zero();
      loop_up_to_zero();
   }
}
`

I tried moving the void functions below main because I am still trying to figure out some of the syntax in C but it did not appear to have much of an impact.

>Solution :

In the line usernum2 = usernum you’re trying to assign value in usernum to usernum2. But in usernum there’s no value at that moment, because you’ve only declared the variable usernum, you’ve never defined it. Example of declaration: int usernum;. Example of definition: int usernum = 0;

Also, in your line printf("%d\n", &usernum2); you shouldn’t pass the address, you should pass the value: printf("%d\n", usernum2);