exercise10.c

#include <stdio.h>

int main(int argc, char *argv[])
{
  if (argc!=2)
  {
    printf("Error: You need one argument.\n");
    // Abort program by returning 1:
    return 1;

  }

int i = 0;
for (i = 0; argv[1][i] != '\0'; i++)
{
  char letter = argv[1][i];
  switch (letter)
  {
    case 'a':
    case 'A':
      printf("%d: 'A'\n", i);
      break;

    case 'e':
    case 'E':
      printf("%d: 'E'\n", i);
      break;

    case 'i':
    case 'I':
      printf("%d: 'I'\n", i);
      break;

    case 'o':
    case 'O':
      printf("%d: 'O'\n", i);
      break;

    case 'u':
    case 'U':
      printf("%d: 'U'\n", i);
      break;

    case 'y':
    case 'Y':
      if (i > 2)
      {
          printf("%d: 'Y'\n", i);
      }
      break;
// If you don't make default statement, it only prints vowels and disregards the other letters.
      default:
        printf("%d: %c is not a vowel\n", i, letter);

    }

}
return 0;
}