View Compilation Error

495888_0_0_20652.c: In function `main':
495888_0_0_20652.c:7: error: `sum' undeclared (first use in this function)
495888_0_0_20652.c:7: error: (Each undeclared identifier is reported only once
495888_0_0_20652.c:7: error: for each function it appears in.)