Convert Vowels into Upper Case in C++

Here is a program is given to us by my friend Tom. This program asks the user to give a string and then the program will convert all the vowels into upper case format in the given string.

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Sample Program Output

#include <iostream>
#include <string>
#include <cctype>

using namespace std;

bool is_vowel(char ch)
   const string vowels("aeiouAEIOU");

   return vowels.find(ch) != string::npos;

string& vowels_to_upper(string& s)
   for (char &ch : s)
     if (is_vowel(ch) && islower(ch))
       ch = toupper(ch);

   return s;

int main()
   string input;

   cout <<"\n\n";
   cout << "\tConvert Vowels into Upper Case in C++";
   cout <<"\n\n";
   while (true)
     cout << "\tEnter a string (or quit): ";
     getline(cin, input);
     if (input == "quit")
     cout <<"\t" <<vowels_to_upper(input) << '\n';
    cout <<"\n";
   cout <<"\n";
   cout <<"\tEnd of Program";
   cout <<"\n";