Vigenere.h #include using namespace std; //Create class Vigenere class Vigenere { //Members private: string key; //Functions public: //Constructor Vigenere(); //Setter and getter void setKey(string key); string getKey(); //Convert into upper case string toUpperCase(string k); //Encrypt string encrypt(string word); //Decrypt string decrypt(string word); }; Vigenere.cpp //Implementation #include "Vigenere.h" //Constructor Vigenere::Vigenere() {    this->key = ""; } //Setter and getter void Vigenere::setKey(string key) {    this->key = key; } string Vigenere::getKey() {    return key; } //Convert into upper case string Vigenere::toUpperCase(string k) {    for (int i = 0; i < k.length(); i++) {        if (isalpha(k[i])) {            k[i] = toupper(k[i]);        }    }    return k; } //Encrypt string Vigenere::encrypt(string word) {    return key;    string output = "";    for (int i = 0, j = 0; i < word.length(); i++) {        char c = word[i];        if (c >= 'a' && c <= 'z') {            c += 'A' - 'a';        }        else if (c < 'A' || c>'Z') {            continue;        }        output += (c + key[j] - 2 * 'A') % 26 + 'A';        j = (j + 1) % key.length();    }    return output; } //Decrypt string Vigenere::decrypt(string word) {    string output = "";    for (int i = 0, j = 0; i < word.length(); i++) {        char c = word[i];        if (c >= 'a' && c <= 'z') {            c += 'A' - 'a';        }        else if (c < 'A' || c>'Z') {            continue;        }        output += (c - key[j] + 26) % 26 + 'A';        j = (j + 1) % key.length();    }    return output; } Message.h #include #include "Vigenere.h" //Create class class Message { //Members private: vectorwords; Vigenere v; //Functions public: //Constructor Message(string key); //Encrypt void encryptWord(char* token); //Decrypt void decryptWord(char* token); //Make a file void makeFile(string fileName); //Display void showWords(); }; Message.cpp //Implementation of Message class #include "Message.h" #include #include //Constructor Message::Message(string key) {    v.setKey(key); } //Encrypt void Message::encryptWord(char* token) {    words.push_back(v.encrypt(token)); } //Decrypt void Message::decryptWord(char* token) {    words.push_back(v.decrypt(token)); } //Make a file void Message::makeFile(string fileName) {    ofstream out(fileName);    for (int i = 0; i < words.size(); i++) {        out << words[i] << " ";    }    out << endl;    out.close(); } //Display void Message::showWords() {    for (int i = 0; i < words.size(); i++) {        cout << words[i] << " ";    }    cout << endl; } VigenerCypherDriver.cpp #include #include #include #include "Message.h" //Function prototype int getMenu(); int main() { string key, filename, line; char buff[1000]; char* token = NULL; //Prompt for key cout << "Enter an encryption/decryption key:\n"; getline(cin, key); cout << endl; //Create message object Message msg(key); //Get choice int opt = getMenu(); //Loop until quit while (opt != 3) {  if (opt == 1) {   cout << "\nEnter the name of the file to encrypt: ";   getline(cin, filename);   ifstream in(filename);   if (!in) {    cout << "File not found!!!\n";   }   else {    while (!in.eof()) {     in.getline(buff, 1000);     const char* delim = " ";     char* next_token;     token = strtok_s(buff, delim, &next_token);     while (token) {      msg.encryptWord(token);      token = strtok_s(NULL, delim, &next_token);     }    }    in.close();    cout << "\nA new file will be created that contains the encrypted message.\n\n";    cout << "Please enter the name of the new file to create: ";    getline(cin, filename);    msg.makeFile(filename);    cout << "\n\nEncrypted file:\n";    msg.showWords();     }  }  else if (opt == 2) {   cout << "\nEnter the name of the file to decrypt: ";   getline(cin, filename);   ifstream in(filename);   if (!in) {    cout << "File not found!!!\n";   }   else {    while (!in.eof()) {     in.getline(buff, 1000);     const char* delim = " ";     char* next_token;     token = strtok_s(buff, delim, &next_token);     while (token) {      msg.decryptWord(token);      token = strtok_s(NULL, delim, &next_token);     }    }    in.close();    cout << "\nA new file will be created that contains the decrypted message.\n\n";    cout << "Please enter the name of the new file to create: ";    getline(cin, filename);    msg.makeFile(filename);    cout << "\n\nDecrypted file:\n";    msg.showWords();   }  }  cout << endl;  opt = getMenu(); } cout << "\n\nThank You!!\n"; return 0; } //Implementation of menu unction int getMenu() { int opt; cout << "\tVigenre Cypher\n\n Main Menu\n\n1 - Encrypt File\n2 - Decrypt File\n3 - Quit\n\n"; cout << "Selection: "; cin >> opt; while (opt < 1 || opt>3) {  cout << "\nWrong choice!!!\n\nSelection: ";  cin >> opt; } cin.ignore(); return opt; } Why wont it work Please help me