View Compilation Error

463815_0_0_22830.c: In function `main':
463815_0_0_22830.c:19: error: `num' undeclared (first use in this function)
463815_0_0_22830.c:19: error: (Each undeclared identifier is reported only once
463815_0_0_22830.c:19: error: for each function it appears in.)