My solution to CS50 pset2 - "Hail, Caesar!" (using function)

caesar2.c

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

/**
 * Caesar.c
 * A program that encrypts messages using Caesar’s cipher. Your program must
 * accept a single command-line argument: a non-negative integer. Let’s call it
 * k for the sake of discussion. If your program is executed without any
 * command-line arguments or with more than one command-line argument, your
 * program should yell at the user and return a value of 1.
 * 
 * */
 
 
 // function that encrypts a character based on the key submitted
 int encryptCode(char code, int key)
 {
    if islower(code)
    {
        code = ((((code + key) - 97) % 26) + 97);
        return code; 
    }
    else if isupper(code)
    {
        code = ((((code + key) - 65) % 26) + 65);
        return code;
    }   
    
    //if neither then just return whatever it is
    else
        return code;
 }
 
 
 int main(int argc, string argv[])
 {
    // check for 2 arguments only
    if (argc != 2)
    {
        printf("Nope\n");
        return 1;
    }
    
    // once I check for correct argv put key into an int k
    int k = atoi(argv[1]);

    // check if the integer is non-negative
    if (k < 0)
    {
        printf("Nope\n");
        return 1;
    }
    else
    {
        // prompt user for a code to encrypt
        string code = GetString();
        
        for (int i = 0, n = strlen(code); i < n; i++)
            {
                printf("%c", encryptCode(code[i], k););
            }
            printf("\n");
            return 0;
    }
 }

Line 63 can just be: printf("%c", encryptCode(code[i], k));