Silvanoshei

Hi gang, I have a Master-slave D flip-flop with Clear and Preset in front of me. I'm a little confused on the output (which is Q and ~Q). If I understand this correctly, when the clock is coming down, negative edge, the input D matters and Q changes. Assuming Q starts at 0, If the clk is 0 and D is 1, that means Q is always 0 unless clk changes to 1... then Q changes to 1 ONLY if clk changes to 0 again and D remains 1? Then following this example D changes to 0, unless clk goes into a negative edge it wont change Q? My next question is the clear and preset, do these override clk and D? From what I read a positive edge flip flop will change the output Q instantly with no regard for the clock. Finally, preset and preset_n are just not opposites yes? My book refers to preset but labels the input Preset_n? I wish my book showed me a example of a timing diagram of this circuit in action.