C Character and String Helpers

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>

int main(void) {
  char text[] = "Hello, World 42!";
  int letters = 0, digits = 0, spaces = 0;
  for (int i = 0; text[i] != '\0'; i++) {
    if (isalpha((unsigned char)text[i])) letters++;
    else if (isdigit((unsigned char)text[i])) digits++;
    else if (isspace((unsigned char)text[i])) spaces++;
  }
  printf("letters=%d digits=%d spaces=%d\n", letters, digits, spaces);

  for (int i = 0; text[i]; i++) text[i] = toupper((unsigned char)text[i]);
  printf("%s\n", text);

  printf("%d\n", atoi("123") + 1);
  printf("%.1f\n", atof("2.5") * 2);
  char *comma = strchr(text, ',');
  printf("comma at %ld\n", (long)(comma - text));
  return 0;
}

letters=10 digits=2 spaces=2
HELLO, WORLD 42!
124
5.0
comma at 5