Example 1 : Calculates the number of vowels in a string

#include <iostream>
#include <cstring>
using namespace std;

int main() {
  int a,b;
  char word[100];

  cout << "Enter a word \n";
  cin >> word;
  a=0; b=0;

  while (word[a] != '\0') {
    switch (word[a]) {
    case 'a': case 'A': b++; break;
    case 'e': case 'E': b++; break;
    case 'i': case 'I': b++; break;
    case 'o': case 'O': b++; break;
    case 'u': case 'U': b++; break;
    }

    a++;
  }
  
  cout << "Number of vowels in the word \"" << word << "\" is " << b << "\n";
  cout << "Number of characters in it is " << a << "\n"; 
  cout << "Check if the above number is the same as "<< strlen(word) << "\n";
  return 0;
}

Example 2: Does the same thing as (1) but does not use "switch".  When there 
is a large number of conditions to be checked (like in this example) the switch
statement is preferable. So (in my opinion) this is a bad program.

#include <iostream>
#include <cstring>
using namespace std;

int main() {
  int a,b=0;
  char word[100];
  
  cout << "Enter a word \n";
  cin >> word;
  for(a=0; a<strlen(word); a++) {
    if ( (word[a] == 'a') || (word[a] == 'A') ||
	 (word[a] == 'e') || (word[a] == 'E') ||
	 (word[a] == 'i') || (word[a] == 'I') ||
	 (word[a] == 'o') || (word[a] == 'O') ||
	 (word[a] == 'u') || (word[a] == 'U') )
      b++;
  }

  cout << "The number of vowels in the word \"" << word << "\" is ";
  cout << b << "\n";

  return 0;
}