Code

 Header...
//
// Count the number of letters, digits, punctuation
// characters and spaces in a well-known phrase
//
 void countem(const char string[]){
   ... 

»  int alphas=0, digits=0, spaces=0, punct=0, others=0;
»  int i;

»  for (i=0; stringi; ++i) {
»    if (isalpha(stringi)) 
      ++alphas;
    else if (isdigit(stringi)) 
      ++digits;
    else if (isspace(stringi)) 
      ++spaces;
    else if (ispunct(stringi)) 
      ++punct;
    else 
      ++others;
  }

»  printf("The string: %s\n"
   "contains %d letters, %d digits, %d spaces,\n"
   "%d punctuation characters and %d other characters\n", 
   string, alphas, digits, spaces, punct, others);
}

 int main(){
   ... 

»  char hello[]="Hello, world";
»  countem(hello);
»  return 0;
}