Code:// Converts plain text to cipher text for (int l = 0, o = strlen(s); l < o; l++) { if (islower(s[l])) { int m = (l % strlen(argv[1])); char c = ((s[l] + shift(argv[1][m]) - 97) % 26 + 97); printf("%c", c); m++; } else if (isupper(s[l])) { int m = (l % strlen(argv[1])); char c = (s[l] + shift(argv[1][m]) - 65) % 26 + 65; printf("%c", c); m++; } else { char c = s[l]; printf("%c", s[l]); }