How do you get a file in C++?

Question

So the teacher has posed this assignment:

You have been hired by the United Network Command for Law Enforcement, and you have been given files containing null cyphers yo

Answer 1

I figured it out! To be honest no one answer helped, it was a combination of the three, plus the comments from them. Thank you all very much! I've attached the code I used, as well as a copy of the document. The program reads in every character, then spits out the deciphered text. (IE: 1h.e0l/lqo is hello) The next step (extra credit) is to set it up so the user inputs how many characters to skip before reading in the next character to input.

This step I intend to do on my own, but again, thank you very much for all the assistance everyone! Proving once again how awesome this site is, one line of code at a time!

EDIT:: Code adjusted to accept user input, as well as allow for multiple uses without recompiling (I realize it looks like a huge sloppy mess, but that's why it's EXTREMELY commented...because in my mind it looks nice and neat)

#include
#include   //used for reading/writing to files, ifstream could have been used, but used fstream for that 'just in case' feeling.
#include    //needed for the filename.
#include   //for goto statement

using namespace std;

int main()
{
    program:
    char choice;  //lets user choose whether to do another document or not.
    char letter;  //used to track each character in the document.
    int x = 1;    //first counter for tracking correct letter.
    int y = 1;    //second counter (1 is used instead of 0 for ease of reading, 1 being the "first character").
    int z;        //third counter (used as a check to see if the first two counters are equal).
    string filename;    //allows for user to input the filename they wish to use.
    cout << "Please make sure the document is in the same file as the program, thank you!" << endl << "Please input document name: " ;
    cin >> filename; //getline(cin, filename);
    cout << endl;
    cout << "'Every nth character is good', what number is n?: ";
    cin >> z;   //user inputs the number at which the character is good. IE: every 5th character is good, they would input 5.
    cout << endl;
    z = z - 1;  //by subtracting 1, you now have the number of characters you will be skipping, the one after those is the letter you want.
    ifstream infile(filename.c_str()); //gets the filename provided, see below for incorrect input.
    if(infile.is_open()) //checks to see if the file is opened.
    {
        while(!infile.eof())    //continues looping until the end of the file.
        {   
                infile.get(letter);  //gets the letters in the order that that they are in the file.
                if (x == y)          //checks to see if the counters match...
                {
                    x++;             //...if they do, adds 1 to the x counter.
                }
                else
                {
                    if((x - y) == z)            //for every nth character that is good, x - y = nth - 1.
                    {
                        cout << letter;         //...if they don't, that means that character is one you want, so it prints that character.
                        y = x;                  //sets both counters equal to restart the process of counting.
                    }
                    else                        //only used when more than every other letter is garbage, continues adding 1 to the first
                    {                           //counter until the first and second counters are equal.
                        x++;
                    }
                }
        }
        cout << endl << "Decryption complete...if unreadable, please check to see if your input key was correct then try again." << endl;
        infile.close();
        cout << "Do you wish to try again? Please press y then enter if yes (case senstive).";
        cin >> choice;
        if(choice == 'y')
        {
            goto program;
        }
    }
    else  //this prints out and program is skipped in case an incorrect file name is used.
    {
        cout << "Unable to open file, please make sure the filename is correct and that you typed in the extension" << endl;
        cout << "IE:" << "     filename.txt" << endl;
        cout << "You input: " << filename << endl;
        cout << "Do you wish to try again? Please press y then enter if yes (case senstive)." ;
        cin >> choice;
        if(choice == 'y')
        {
            goto program;
        }
    }
    getchar();  //because I use visual C++ express.
}

EDIT:::

I tried inserting the text, but I couldn't get it to come out right, it kept treating some of the characters like coding (ie an apostrophe apparently is the equivalent of the bold command), but you could just try putting in "0h1e.l9lao" without the parenthesis into a .txt and it should give the same outcome.

Thanks again everyone for the help!