Convert Integer to String

Question

Problem: Convert Integer to String. Solve this hands-on electronics task on EWskills.

Accepted Answer

#include 

// Convert integer to string and print each character with space
void print_integer_as_string(int num) {
    if (num == 0) {
        printf("0");
        return;
    }

    char buffer[12];  // Enough for -32768 to 32767
    int i = 0;
    int is_negative = 0;

    if (num < 0) {
        is_negative = 1;
        num = -num;
    }

    // Convert digits in reverse
    while (num > 0) {
        buffer[i++] = (num % 10) + '0';
        num /= 10;
    }

    if (is_negative) {
        buffer[i++] = '-';
    }

    // Print characters in reverse order with space
    for (int j = i - 1; j >= 0; j--) {
        printf("%c", buffer[j]);
        if (j > 0) printf(" ");
    }
}

int main() {
    int num;
    scanf("%d", &num);
    print_integer_as_string(num);
    return 0;
}

Why It’s Important in Firmware?

Required for displaying numbers on UART, LCD, or serial logs
Avoids dependency on heavy libraries in bare-metal systems
Builds deep understanding of integer encoding and display formatting

Solution Logic

Handle Zero Case Directly
If the input number is 0, we immediately print "0" and return.
This avoids extra logic for zero inside the main loop.
Check for Negative Numbers
If the input number is negative:
- Set a flag is_negative = 1
- Convert it to positive by negating (num = -num)
- This allows us to treat all digits uniformly in the next steps.
Extract Digits from Least Significant to Most
- Use a loop: num % 10 gives the last digit
- Convert digit to character: add '0' → (num % 10) + '0'
- Store each digit in a buffer in reverse order (from least to most significant)
Append Negative Sign if Needed
- If the original number was negative, add '-' to the buffer after digits
Print Characters in Reverse
- Since digits were stored in reverse, we loop backward through the buffer
- Print each character, with a space between them for clarity

117. Convert Integer to String