a) a combinational logic device
b) a sequential logic device

Can someone please explain to me what are the operational differences between the two ? oh yeah and one more thing ,

what is a tri state device ?

 

Combinational logic: many gates tied together, current output depends only on current input
Sequential logic: composed of combinational logic, but has memory; thus, outputs depend on previous inputs. Can be split into moore or mealy machines, Moore is when it depends on the current state (not current input), and Mealy is when it depends on current state and current input.

Tristate means there are three states, typically, low, high, and hi-Z

Steve

 

The hi-Z state output allows a logic device to switch itself out of a circuit, which allows it to share a buss (as in a computer buss) with other devices.