View Compilation Error

0_0_8305123_20178.c: In function `main':
0_0_8305123_20178.c:5: error: `bool' undeclared (first use in this function)
0_0_8305123_20178.c:5: error: (Each undeclared identifier is reported only once
0_0_8305123_20178.c:5: error: for each function it appears in.)
0_0_8305123_20178.c:5: error: syntax error before "flag"
0_0_8305123_20178.c:12: error: `flag' undeclared (first use in this function)
0_0_8305123_20178.c:12: error: `true' undeclared (first use in this function)