Looping back to the beginning of the alphabet after z

Question

I am working on a problem for school, and I have to write a program that rotates 13 characters. I have the program done, but it rotates into some weird characters. I want to make it look back to 'a' after it reaches 'z' for both uppercase and lowercase. Basically, I want to restrict my options to A-Z and a-z.

Tried a mixture of while statements and if statements, and ended up on with just some if statements. I know they are wrong, but it runs in its current state.

#include <iostream>
using namespace std;

//Function Prototypes
char rot(char c);
int mylen(char c[]);

int main()
{
    char in[120], out[120];
    int i;  // index into in

    cout << "Enter text: ";
    cin.getline(in,120);
    while (strcmp(in, "exit"))
    {
        for (i = 0; i < mylen(in); i++)
        {
            out[i] = rot(in[i]);
        }
        out[i++] = '\0';

        cout << out << endl;
        cout << endl << "Enter some more text: ";
        cin.getline(in,120);
    }


    return 0;
}

char rot(char c)
{
        if (c >= 'a' and c <= 'z')
        c = c + 13;

    if (c > 'z')
        c = c - 26;


else if (c >= 'A' and c <= 'Z')

        c = c + 13;

    if (c > 'Z')
        c = c - 26;

    return c;
}

int mylen(char c[])
{
    int cnt = 0;

    while (c[cnt] != '\0')
        cnt++;

    return cnt;
}

I am looking just to have it rotate 13 characters, and when someone inputs rotated code, to rotate it again 13 characters.

Answer 1

I suggest you should carefully observe the table of ASCII code to display the character.There are 6 characters between the uppercase letter "A"~"Z" and the lowercase letter "a"~"z"

Here is my code:

if (c >= 'n' && c <= 'z')
    {
        c = c - 13;
    }
    else if (c >= 'a' && c <= 'm')
    {
        c = c + 13;
    }

    if (c >= 'N' && c<='Z')
    {
        c = c - 13;
    }

    else if (c >= 'A' && c <= 'M')
    {
        c = c+13;
    }