View Compilation Error

54728_0_22051.c: In function `main':
54728_0_22051.c:6: error: `bool' undeclared (first use in this function)
54728_0_22051.c:6: error: (Each undeclared identifier is reported only once
54728_0_22051.c:6: error: for each function it appears in.)
54728_0_22051.c:6: error: syntax error before "flag"
54728_0_22051.c:9: error: `flag' undeclared (first use in this function)
54728_0_22051.c:9: error: `false' undeclared (first use in this function)
54728_0_22051.c:22: error: `true' undeclared (first use in this function)