Convert Uppercase Letters to Lowercase

Code

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

int is_upper(uint8_t ch) {
    return (ch >= 'A' && ch <= 'Z');
}

void to_lowercase(char *str) {
    while (*str) {
        if (is_upper(*str))
            *str = *str - 'A' + 'a';
        *str++;
    }
}

int main() {
    char str[101];
    fgets(str, sizeof(str), stdin);

    // Remove newline
    uint8_t i = 0;
    while (str[i]) {
        if (str[i] == '\n') {
            str[i] = '\0';
            break;
        }
        i++;
    }

    to_lowercase(str);
    printf("%s", str);
    return 0;
}

Solving Approach