There are 16 data outputs of the ALU, collectively called ALU-OUT. The condition outputs C, N, Z and V of the ALU signify the following conditions.

C     Final carry-out of the adder is 1;
      signifies overflow if the contents of
      the registers are considered to be unsigned.
V     Overflow of 2's complement numbers
Z     All output wires have 0
N     The value is negative when viewed as a 2's
      complement number (ALU-OUT15=1)