caesar

#include <cs50.h>
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>

int main(int argc, string argv[1])
{

    int key = atoi(argv[1]); //user input at start of program

    if (argc != 2 || key < 1) //if user doesn't run command-line argument of one or enter positive int
    {
        printf("Usage: ./caesar key\n"); //prompt them to run it again
        return 1; //returning zero means everything went well
    }

    string s = get_string("plaintext: "); //prompt for plaintext
    for (int i = 0; i < strlen(s); i++) //length of the entire string

    string cipher = [(((s[i] - 97) + key) % 26) + 97;]; //create new string, add key and rotate
    for (int j = 0; j < strlen(s); j++)

        if isupper(s[i])
            char c = [(((s[i] - 65) + key) % 26) + 65;]

        if islower(s[i])
            char c = [(((s[i] - 97) + key) % 26) + 97;]
    {
        printf("ciphertext: %c\n", cipher[j]); //print new string after rotating
    }
    return 0;
}