c - Caesar Cipher shifting characters -

i had received assignment last month , ended getting wrong because of problem state after this. currently, doing caesar's cipher , believe have right format. ask user string , encrypted key == 3. however, want loop around alphabet if plaintext letter x, y, z, x, y, or z. but, when put of characters in, not a, b, , c, ]... , other braces. hints fix problem. thank you!

void main() {         int key = 3;      char string[256];     int = 0;      printf("enter string want encrypted\n");     fgets(string, sizeof(string), stdin);      (i = 0; < strlen(string); i++) {         if (string[i] == ' ') {;}          else if  ((string[i] >= 'a' && string[i] <= 'z' || string[i] >= 'a' && string[i] <= 'z')){                 string[i] = string[i] + key;         }     }     printf("cipher text:%s",string); } 

you need @ ascii table: http://www.asciitable.com/. you're using ascii encoding of characters.

z has decimal value of 90, 93 ']'. need manually wrap around beginning of alphabet. best done modulo , adding ascii value of first alphabetic character. it's how wrap capital letters (back 'a' or 'a').