Semiconductor Electronics Part 2

The given circuit can be drawn as
The output, Z=A.B
=A+B
(Using de-Morgan theorem)
This is the expression of a NOR gate. So, the logic operation carriedout by the given circuit is NOR.
Alternate Method
The given question can be solved using truth table, which is as given below

A	B	X	Y	Z
0	0	1	1	1
1	1	0	0	0
1	0	0	1	0
0	1	1	0	0

This truth table is similar to that of a NOR gate.