Why is my to_base_n Program not working? - c

Question

I need to write a C program which will read a number (in base 10) from user input and output it in any base which is a power of 2. The calculations have to be performed in one function, to_base_n, which takes the parameters num and base and prints the number in the respective base. As a validation check, the program also checks if the base is a power of two with the isPowerofTwo function.
The way the conversion is carried out is by means of long division which carries out the logic in the pseudocode below:
void to_base_n(int x, int n){
int r, i = 0
int digits[16]
while (x ≠ 0){
r = x mod n
x = x / n
digits[i] = r
i++
}
for (i = 0, i < 15, i++)
print digits[i]
}
Which I believe is arithmetically sound. But when I try to, for example, convert 82000 to base 4, I get the following output:
The large digits appearing are even bigger than num itself, so I figured the modulus cannot be entering the array properly (because ∀{x,n}; x mod n < x). I can't seem to find what's wrong with it. The full code is listed below.
#include <stdio.h>
#include <ctype.h>
#include <stdbool.h>
bool isPowerofTwo(int);
void to_base_n(int, int);
int main(){
//Variables
int num, base;
//Prompt
printf("Please enter a number in base 10: ");
scanf("%d", &num);
printf("Please enter a base (2^n) to convert it to: ");
scanf("%d", &base);
//Precaution
while(!isPowerofTwo(base)){
printf("That number is not a power of 2. Please try again: ");;
scanf("%d", &base);
}
if(isPowerofTwo(base)){
//Output
printf("The number %d (base 10) is equivalent to ", num);
to_base_n(num, base);
printf(" (base %d).", base);
}
//Return Statement
return 0;
}
//Checks if Base is a Power of Two
bool isPowerofTwo(int base){
while((base % 2 == 0) && base > 1){
base = base / 2;
if(base == 1){
return true;
break;
}
}
return false;
}
//to_base_n
void to_base_n(int x, int n){
int r, i = 0;
int digits[16];
while(x != 0){
r = x % n;
x = x / n;
digits[i] = r;
i++;
}
for(i = 0; i < 15; i++)
printf("%d|",digits[i]);
}
Can anyone help explain what's wrong with it?

Answer 1

The number 82000 in base 4 would be:
110001100
Which is exacly what you get. Your mistake is that:
They are printed backwards.
You are printing more digits than you should, so you print garbage.

Answer 2

You ignore the number of digits extracted with your pseudo code, so you print uninitialised elements of the array.
for (i = 0, i < 15, i++)
print digits[i]
And they are printed in reverse order. I suggest changing it to this
for (i = i - 1, i >= 0, i--)
print digits[i]
and as C code in your function
for(i = i - 1; i >= 0; i--)
printf("%d|",digits[i]);