vowe.c

#include <stdio.h>

int count_vowe(const char *text) {
  const char *ch = text;
  int count = 0;

  for (; *ch != '\0'; ch++) {
    switch (*ch) {
    case 'a':
    case 'e':
    case 'i':
    case 'o':
    case 'u':
    case 'A':
    case 'E':
    case 'I':
    case 'O':
    case 'U':
      count++;
    }
  }

  return count;
}

int main(void) {
  printf("vowe = %d\n", count_vowe("aeiou"));
  return 0;
}