Thread: Islower, isupper

Hi, I'm busy with an exercise for a course. Ik have to make ap program that codes tekst by changing the letters from the alphabet. f.e. Key = 2, so a is c and l is n etcetera.

Now I want the uppercase letters tot remain uppercase ande the lowercase letters lowercase. I thought I had a nice solution, but it doesn't work. What am I doing wrong?

insert

Code:

#include <cs50.h>
#include <stdio.h>
int main(void)
{
    int key;
    //get key//
    do {
    printf("Enter your key (0-26)\n");
    key=get_int();
    }
    while (key<0 || key>26);
    //get plaintext//
    char text[50];
    printf("Enter your massage (max 50 characters): ");
    fgets(text, sizeof(text), stdin);
    //encipher//
    int x;
    for(x=0;x<50;x++)
        {
            if (isupper(text[x]))
            {
                printf("%c",(text[x]+key)%97);
            }
            else if (islower(text[x]))
            {
                printf("%c",(text[x]+key)%65);
            }
            else
            {
                break;
            }
        }
return(0);
}