View Compilation Error

0_0_6228048_2636.c: In function `main':
0_0_6228048_2636.c:6: error: `bool' undeclared (first use in this function)
0_0_6228048_2636.c:6: error: (Each undeclared identifier is reported only once
0_0_6228048_2636.c:6: error: for each function it appears in.)
0_0_6228048_2636.c:6: error: syntax error before "flag"
0_0_6228048_2636.c:13: error: `flag' undeclared (first use in this function)