Analog to digital converter

hello everyone!!
i just wanna know what is the purpose of the gates(and,or,inverter) in this circuit?it is for bits?

Im just new..

thanks for the help..


also the gates are:

AND 74ls08
OR 74ls32
INVERTER 74ls04

analog in out of comp. out of logic
0v to 0.75v 0,0,0 00
0.75v to1.5v 1,00 01
1.5v to 2.25v 1,1,0 10
2.25v to 1,1,1 11