Tic tac toe in C.

ttt.c

/* Tic tac toe in C. */
#include <stdio.h>
#define P printf
enum { X = 'X', O = 'O', N = '\0', C = 'C' };
static char ck(char b[9]) {
  int i, w[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 0, 3, 6,
                1, 4, 7, 2, 5, 8, 0, 4, 8, 2, 4, 6};
  for (i = 0; i < 24; i += 3) {
    if (b[w[i + 0]] == X && b[w[i + 1]] == X && b[w[i + 2]] == X) return X;
    if (b[w[i + 0]] == O && b[w[i + 1]] == O && b[w[i + 2]] == O) return O;
  }
  for (i = 0; i < 9; i++) if (b[i] == N) return N; return C;
}
#define S(i)                                                           \
  (b[i] == X ? "\033[1;32mX\033[m" : b[i] == O ? "\033[1;34mO\033[m" : ".")
#define B                                                              \
  P("\n╭─┬─┬─╮\n│%s│%s│%s│ 0 1 2\n├─┼─┼─┤\n│%s│%s│%s│ 3 4 5\n"         \
    "├─┼─┼─┤\n│%s│%s│%s│ 6 7 8\n╰─┴─┴─╯\n",                            \
    S(0), S(1), S(2), S(3), S(4), S(5), S(6), S(7), S(8));
int main() { char b[9] = {N}, *res, l[32], p = X, w = N; int m, t = 1; B;
  do { while (1) {
      P("\nTurn #%d. %c, your move (0-8): ", t, p);
      fflush(stdout); res = fgets(l, sizeof l, stdin);
      if (!(res == l &&
            (sscanf(l, "%d", &m) != 1 || m < 0 || m > 8 || b[m] != N)))
        break;
    };
    t++; b[m] = p; B; p = (p == X) ? O : X; w = ck(b);
    if (w == C) { P("\ndraw.\n"); } else if (w != N) { P("\n%c won.\n", w); }
  } while (w == N); fflush(stdout); return 0;
}

Minimalistic Tic Tac Toe in C. Download ttt.c, compile and run:

wget -c hhttps://gist.githubusercontent.com/koppi/33eed584ea3b6a9f43d5c30911ee1d46/raw/2170c5d21f2c552374a2b9442e25dfeeb8d09a11/ttt.c
make ttt
./ttt

The game:

After some moves: