97. Convert Decimal Number to Binary or Hex Without itoa function

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

// Print num in binary or hex without using itoa/sprintf
void print_base(uint16_t num, uint8_t base) {
    if (num == 0) {
        printf("0");
        return;
    }

    char digits[17] = "0123456789ABCDEF";
    char buffer[20]; // Enough to hold result
    int i = 0;

    while (num > 0) {
        buffer[i++] = digits[num % base];
        num /= base;
    }

    // Print in reverse
    for (int j = i - 1; j >= 0; j--) {
        putchar(buffer[j]);
    }
}

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

    print_base(num, base);
    return 0;
}

Why This Matters in Firmware?

• itoa()/sprintf() are often not available or waste memory
• Needed for serial data formatting (e.g. binary config display, debug logs)

Logic Summary

• Convert num % base to a digit (0–9, A–F)
• Store in buffer in reverse
• Print characters in reverse order