View Compilation Error

218630_0_20042.c: In function `main':
218630_0_20042.c:9: error: `bool' undeclared (first use in this function)
218630_0_20042.c:9: error: (Each undeclared identifier is reported only once
218630_0_20042.c:9: error: for each function it appears in.)
218630_0_20042.c:9: error: syntax error before "flag"
218630_0_20042.c:15: error: `flag' undeclared (first use in this function)