Big Band testing output of the given system?

I have done studying top down , bottom up and sandwich approaches of software testing on the below diagram but i am little confused regarding big bang testing can you explain big bang testing that how it should be performed on the below system so i understand its working better

                          A
                       /  |   \
                     B    C     D
                    |    / \    |
                   E1   E2  F1  F2
                    |   |    |   |
                   G1   G2   G3  G4

What will be the big bang output ?