caesar.c - shared from CS50 IDE

caesar.c

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

int c;
int k;

int main(int argc, string argv[]) {
    if (argc == 0 || argc >2) {
        printf ("ERROR\n");
       return 1;
    }
     k = atoi(argv[1]);
     
     string p = GetString();
     printf("plaintext: %s\n", p);
     printf ("ciphertext: ");
     
     
     for (int i = 0, n = strlen(p); i < n; i++) {
            
            if (isalpha (p[i])) {
                c = (p[i] + k)%26;
                printf ("%c", (char) c);
            }
     
            
            
          
         }
         
 

}