can someone tell me how this program works? I'm trying to learning C++ by reading some examples, and this one is one of them.
[CODE]#include <iostream>

include <string>

using namespace std;

class Vigenere
{
public:
string key;

Vigenere(string key)
{
for(int i = 0; i < key.size(); ++i)
{
if(key[i] >= 'A' && key[i] <= 'Z')
this->key += key[i];
else if(key[i] >= 'a' && key[i] <= 'z')
this->key += key[i] + 'A' - 'a';
}
}

string encrypt(string text)
{
string out;

for(int i = 0, j = 0; i < text.length(); ++i)
{
  char c = text[i];

  if(c >= 'a' && c <= 'z')
    c += 'A' - 'a';
  else if(c < 'A' || c > 'Z')
    continue;

  out += (c + key[j] - 2*'A') % 26 + 'A'; 
  j = (j + 1) % key.length();
}

return out;

}

string decrypt(string text)
{
string out;

for(int i = 0, j = 0; i < text.length(); ++i)
{
  char c = text[i];

  if(c >= 'a' && c <= 'z')
    c += 'A' - 'a';
  else if(c < 'A' || c > 'Z')
    continue;

  out += (c - key[j] + 26) % 26 + 'A'; 
  j = (j + 1) % key.length();
}

return out;

}
};

int main()
{
Vigenere cipher("VIGENERECIPHER");

string original = "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!";
string encrypted = cipher.encrypt(original);
string decrypted = cipher.decrypt(encrypted);

cout << original << endl;
cout << "Encrypted: " << encrypted << endl;
cout ...

Anuradha Mandal commented: Not easy start. +0