Question

I am trying to create a Caesar cipher using C++. I have the program read in a text file but I need it to encrypt the text and output to the screen.

This is my encryption code but I can’t seem to get it to work. I have only just started using C++ and not really sure where to go from here.

cout << "enter a value between 1-26 to encrypt the text: ";
cin >> shift;

while ((shift <1) || (shift >26)) {
    cout << "Enter a value between 1 and 26!: ";
    cin >> shift;
}

int size = strlen(text);
int i=0;

for(i=0; i<size; i++) {
    cipher[i] = (text[i]);
    if (islower(text[i])) {
        if (text[i] > 122) {
            cipher[i] = ( (int)(text[i] - 26) + shift);
        }
    } else if (isupper(text[i])) {
        if (text[i] > 90) {
            cipher[i] = ( (int)(text[i] - 26) + shift);
        }
    }
}

cipher[size] = '\0';
cout << cipher << endl;

Answer 1

reformatted, made compilable ad fixed algorithm (to what i think was tried to achieve)

#include <iostream>
using namespace std;

char text[] = {"This is my encryption code but I can't seem to get it to work. "
               "I have only just started using C++ and not really sure where "
               "to go from here."};
char cipher[sizeof(text)];

void main()
{
    int shift;
    do {
        cout << "enter a value between 1-26 to encrypt the text: ";
        cin >> shift;
    } while ((shift <1) || (shift >26));

    int size = strlen(text);
    int i=0;

    for(i=0; i<size; i++)
    {
        cipher[i] = text[i];
        if (islower(cipher[i])) {
            cipher[i] = (cipher[i]-'a'+shift)%26+'a';
        }
        else if (isupper(cipher[i])) {
            cipher[i] = (cipher[i]-'A'+shift)%26+'A';
        }
    }

    cipher[size] = '\0';
    cout << cipher << endl;
}