Convert Decimal Number to Binary or Hex Without itoa function

#include <stdio.h>
#include <stdint.h>

void print_base(uint16_t num, uint8_t base) {
    int buffer[30];
    if(num == 0){
        printf("0\n");
        return;
    }
    int i = 0;
    while(num > 0){
        int rem = num % base;
        if(rem <= 9){
            buffer[i] = rem + '0';
        }else if(rem > 9){
            buffer[i] = (rem - 10) + 'A';
        }
    i++;
    num /= base;
    }
    for(int j=i-1; j>=0; j--){
        printf("%c",buffer[j]);
    }
}

int main() {
    uint16_t num;
    uint8_t base;
    scanf("%hu %hhu", &num, &base);

    print_base(num, base);
    return 0;
}