Table Lookup

static int vowels[]
   = {1,0,0,0,1,0,0,0,1,0,0,0,0,
      0,1,0,0,0,0,0,1,0,0,0,1,0};

int vowel(ch)
  int ch;
  {  int sw;
     sw = vowels[ch - 'A'];
     return (sw);
   }