A ROT13 function that uses a switch. Simply pass in a string and get the modified string back. wait.h is simply a header I wrote to suspend the program using cin.get();

#include <string>
#include <iostream>
#include "wait.h"

string ROT13(string original)
{
    string result = original;
    for (unsigned int a = 0; a<result.length(); ++a)
    {
        switch (result[a])
        {
            case 'a':
                result[a] = 'n';
                break;
            case 'A':
                result[a] = 'N';
                break;
            case 'b':
                result[a] = 'o';
                break;
            case 'B':
                result[a] = 'O';
                break;
            case 'c':
                result[a] = 'p';
                break;
            case 'C':
                result[a] = 'P';
                break;
            case 'd':
                result[a] = 'q';
                break;
            case 'D':
                result[a] = 'Q';
                break;
            case 'e':
                result[a] = 'r';
                break;
            case 'E':
                result[a] = 'R';
                break;
            case 'f':
                result[a] = 's';
                break;
            case 'F':
                result[a] = 'S';
                break;
            case 'g':
                result[a] = 't';
                break;
            case 'G':
                result[a] = 'T';
                break;
            case 'h':
                result[a] = 'u';
                break;
            case 'H':
                result[a] = 'U';
                break;
            case 'i':
                result[a] = 'v';
                break;
            case 'I':
                result[a] = 'V';
                break;
            case 'j':
                result[a] = 'w';
                break;
            case 'J':
                result[a] = 'W';
                break;
            case 'k':
                result[a] = 'x';
                break;
            case 'K':
                result[a] = 'X';
                break;
            case 'l':
                result[a] = 'y';
                break;
            case 'L':
                result[a] = 'Y';
                break;
            case 'm':
                result[a] = 'z';
                break;
            case 'M':
                result[a] = 'Z';
                break;
            case 'n':
                result[a] = 'a';
                break;
            case 'N':
                result[a] = 'A';
                break;
            case 'o':
                result[a] = 'b';
                break;
            case 'O':
                result[a] = 'B';
                break;
            case 'p':
                result[a] = 'c';
                break;
            case 'P':
                result[a] = 'C';
                break;
            case 'q':
                result[a] = 'd';
                break;
            case 'Q':
                result[a] = 'D';
                break;
            case 'r':
                result[a] = 'e';
                break;
            case 'R':
                result[a] = 'E';
                break;
            case 's':
                result[a] = 'f';
                break;
            case 'S':
                result[a] = 'F';
                break;
            case 't':
                result[a] = 'g';
                break;
            case 'T':
                result[a] = 'G';
                break;
            case 'u':
                result[a] = 'h';
                break;
            case 'U':
                result[a] = 'H';
                break;
            case 'v':
                result[a] = 'i';
                break;
            case 'V':
                result[a] = 'I';
                break;
            case 'w':
                result[a] = 'j';
                break;
            case 'W':
                result[a] = 'J';
                break;
            case 'x':
                result[a] = 'k';
                break;
            case 'X':
                result[a] = 'K';
                break;
            case 'y':
                result[a] = 'l';
                break;
            case 'Y':
                result[a] = 'L';
                break;
            case 'z':
                result[a] = 'm';
                break;
            case 'Z':
                result[a] = 'M';
                break;
        }
    }
    return result;
}

int _tmain(int argc, _TCHAR* argv[])
{
    string a;
    getline(cin, a);
    cout << ROT13(a) << endl;
    wait();
    return 0;
}