Let me give you a list:
The binary of 8 is 1000 The binary of 7 is 0111
1000
0111
In the & operation 1&1=1,1&0=0,0&0=0
And the corresponding operation is calculated according to the position, that is, the first and first operations, other analogies
So 0000 can be obtained, so the output is 0.