View Compilation Error

860759_0_0_20556.c: In function `main':
860759_0_0_20556.c:7: error: `sum' undeclared (first use in this function)
860759_0_0_20556.c:7: error: (Each undeclared identifier is reported only once
860759_0_0_20556.c:7: error: for each function it appears in.)